Mdthbs

Why is it okay to say "get injured" but not "get increased"?

For example:

I got injured yesterday.

My salary got increased yesterday.

I know the second sentence doesn't sound natural and right in English, but I can't figure out what exactly is wrong with it.

My salary got increased yesterday is just as grammatical as I got injured yesterday, or the sky got dark or his feelings got hurt, or in 2018, the Quadrennial Defense Review got replaced by the National Defense Strategy. The last example sounds "funny" just as your salary example does for reasons that are related to idiomacity, not grammaticality.

In informal, conversational English, get is sometimes used as a marker of the passive voice, instead of standard auxiliary be. These are sometimes distinguished as the get-passive and be-passive respectively.

The Voice of America Learning English website has a page on "The Passive Voice with 'Get'" which explains that

The verb get can be followed by some adjectives to express the idea of change or becoming something. We use this structure for people and things.…

Get can also be followed by the past participle…. The verb get expresses action so, for this structure, we use it with action verbs. Action verbs express physical or mental action.

Using get places more emphasis on the subject or the nature of the act itself, and often indicates when something is more or less desired or expected than be might indicate. I got fired is a more intense expression than I was fired; it carries a much stronger connotation of an unwanted, unfair, unexpected, etc. dismissal executed by someone else, whereas I was fired is more clinical.

Although get is common in conversational English, it is also avoided in more formal communication on either side of the pond, particularly in writing. The get-passive, furthermore, tends to be used with simple actions as opposed to complex, planned activities.

All this contributes to my salary got increased sounding a bit off. A salary is an abstraction, so it is a little strange to think of a salary obtaining an increase; it is the employee who has obtained the increase. Salary is also a technical term for a specific form of compensation, suggesting a process that is more involved than something you can get increased. If I may suggest a few alternatives:

My salary was increased.

Using the be-passive is unexceptional.

I got my salary increased.

This emphasizes that the increase is attributable to your intervention.

My pay got bumped up.

This uses the more informal pay and bump up which are more congruent with the informal got.

I got a raise.

This is the most idiomatic way to describe the situation in American English. Here, however, get is used in its active sense of obtaining or receiving something.

I'm going to abuse the notion of active and passive voice here. Active voice is when "An actor does an action" while passive voice is when "An action is done (by someone). "To get" is an action verb, it needs to be performed by an an actor.

"I got injured" is an active-voiced sentence. You, as an animate, sentient being, are capable of getting something, and "injured" is a thing we recognize you could get.

"My salary got increased" feels passive-voiced because "your salary" is not a material thing, it is just a concept or idea and therefore is not capable of "getting" anything. You could certainly say "My salary was increased..." because "was" doesn't require "my salary" to perform an action or "I got a salary increase" because "I" can perform an action.

Tl;dr
While "my salary got increased" is grammatical, it feels wrong because an inanimate thing can't perform the action "to get," is can only "receive"