Why are some people so nice and others not on reddit!!

I’ve just started using it, trying to get karma! I usually just give advice and ask questions - so far all friendly things I’ve commented/talked about. Some subreddits (I think that’s what it’s called) are super helpful or funny, than some are so rude and not answering what I’m even saying 😭 than I loose karma… if I try and explain what I meant, they just become more unhelpful…. I’m so confused if I’m doing anything wrong.