In this article titled "Merkel Didn't Give Johnson 30 Days to Fix Brexit" the author writes

The U.K. has been told time and time again that as soon as a workable
solution is found to the problem of the Irish border, the backstop
won’t be necessary.

Also as far as I understand (but I could be wrong) the backstop would not keep the entire U.K. tied to many of the EU’s customs and trading rules. It could, however, keep Northern Ireland tied to those rules (maybe similar to what might happen to Gibraltar?).

But according to this article, titled "Brexit: Emmanuel Macron tells Boris Johnson the EU will not tear up May deal", Boris Johnson said that

“She [Mrs Merkel] said if we can do this in two years then we can do
this in 30 days and I admire that ‘can-do’ spirit that she seemed to
have and I think she is right. I think that the technical solutions
are readily available and they have been discussed at great length.

“You can have trusted-trader schemes, you can have electronic
pre-clearing for goods moving across the border and I just want to
repeat one crucial thing, under no circumstances will the UK be
putting checks at the frontier.

And this article, titled "U.K.’s Johnson Plays Down Hopes of Quick Brexit Deal With EU", says about Boris Johnson

On Friday, the U.K. leader repeated his view that there were “lots of
ways” to achieve a frictionless border. “But to persuade our EU
friends and partners, who are very, very, very hard over against it,
will take some time,” he said.

So according to Boris Johnson, it seems, there are options that don't require a border. If that is the case then the backstop would automatically be a non-issue and getting stuck on it is inconsistent with these claims.

Based on these factors, why is the U.K. so keen to have the backstop removed?

The problem stems from three issues. I'll explain those, then the backstop issue will be more obvious.

1. Brexit will create two sovereign regions, with (over time) different borders and import rules. This is the express intent of Brexit after all.




2. Where two sovereign regions meet, there needs to be some kind of formal controls over goods and people crossing the line between them, to ensure that the rules of each are met. Obvious again. Otherwise you couldn't keep out defective goods, dangerous/illegal people, or collect required taxes or similar.




3. There is no good place to draw that line, in the Brexit process. Putting it between Northern Ireland and the EU (Eire) breaks or imperils a major and sensitive peace agreement. Putting it between Northern Ireland and the rest of the UK fragments the UK and breaks the UK's (informal?) constitution.

So this is the problem. The UK wants to leave. Leaving requires a UK-EU border line. Nobody can figure how to solve the problem of creating one, without blowing up either the Irish peace agreement or UK unity.

The solution was – as often in politics – to kick the issue into the future. "We will figure this out in depth later". But in case it couldn't be figured out, or "later" took a long time, the agreement reached by Theresa May and the EU says that until a good solution is found (or, if one isn't quickly found), a temporary solution will be applied that keeps Northern Ireland aligned with the EU to protect the peace agreement, and presumably, a customs border between Northern Ireland and the rest of the UK. Or something like that.

And this temporary solution will run as long as needed (years? decades?) until both the UK and EU agree a better solution has been found.

That temporary solution is what the "backstop" actually is.

So with that background, the answer to the question is roughly this:

• Britain wants the backstop removed from the agreement, because as long as the backstop exists, the UK (or part of it) is still bound to EU rules, and can't move on. That's why the UK government wants it removed.


• The government supports this by arguing that other ways can be found (technological?) to fully handle the customs issues, without needing a formal (hard) border to be created. If true, it would indeed mean that the backstop won't be needed. So they feel it can be ditched.


• The problem is that nobody else in the negotiation agrees, and no other country has made such a thing work. Ever. So naturally the EU isn't agreeing that any currently discussed alternative approaches can work as an alternative.


• So the EU feels that there isn't a way to avoid the issues, right now, so for the time being the backstop (or something like it) is needed to be sure their border stays protected until a permanent and actual agreed solution is found. But obviously they can't say how long that would be either.


• So the UK government is arguing that the backstop isn't needed, because solutions can be found, while the EU is saying that solutions haven't yet been found and agreed, and yes it's been agreed they will try to find one, but until they succeed a temporary solution (the backstop) is unavoidable.

The leadership is lying. They know that a border will be required to protect the Single Market, but it's inconvenient for them because they have no solution to it. So they deny it and pretend that it's not needed.

Also as far as I understand (but I could be wrong) the backstop would not keep the entire U.K. tied to many of the EU’s customs and trading rules. It could, however, keep Northern Ireland tied to those rules (maybe similar to what might happen to Gibraltar?).

Northern Ireland and the rest of the UK having different rules is not something unionists want. Especially the Conservatives' coalition party the DUP (Democratic Unionist Party) does not want that. As the BBC puts it:

To the DUP, the backstop represented its worst fears come to life: regulatory differences meaning only NI would continue to follow some EU rules, no time limit and the ability to exit the backstop would need to be agreed jointly by the UK and EU.

And to some extent, this reasoning also goes for the Conservative party, which full name also includes the word unionist, again from the BBC (emphasis mine):

In 1886, the Liberal Party split over the issue of home rule for Ireland, and the Liberal Unionist Party was formed. It formed an alliance with the Tories before being formally absorbed in 1912, creating the full title of the present-day organisation: the Conservative and Unionist Party.

A more realpolitik answer should note that it opens the door of Northern Ireland reuniting with the Republic of Ireland. After all, it would be closer aligned to the Republic than to the rest of the UK, when comparing the current situation to the backstop situation.

The way Irish Unification works is explained in another of my answers. Eventually, it's up to the people of Northern Ireland, and the backstop may be a factor when people make that opinion. Given the previous, that is not something UK unionists want, and losing part of one's territory is not something people want (in general).