Because they think it's a forum where they can ask anything. Not that people can ask them anything. Honest misunderstanding for someone new to Reddit.

People who have never used Reddit, will obviously not know what AMA means.

Investment Manager

Forget the Reddit inspiration. The community name itself is clear no?  
  
 I get your point tho

Software Engineer

I have been seeing this a lot here. There are hardly relevant posts here. Almost every post is just random question that OP didn't know where to put. This community

I have been seeing this a lot here. There are hardly relevant posts here. Almost every post is just random question that OP didn't know where to put. This community is being treated as r/askReddit when actually it should be r/AMA.

Is it just me getting annoyed by this?

Why people use Ask Me Anything community as Answer My Random Question Which doesn't Belong To Any Community?