People who text back something like, "Hey can't talk now gtg bye" after you text "hey" are really annoying. If you can't talk than just don't text back in the first place, amirite?

IMO it's better to get a text back than nothing at all. If they don't reply then you're kinda left hanging.

People who text "hey" are really annoying, amirite?

FTFY

"hey"

-5 hours later-

come on... i would like a reply at least....
-2 more hours later-
"oh. hey"
"FINALLY!"

or

"hey"
"cant talk atm busy gtg kthxbai"
"k"
-doesnt have to wait now-

I say those kind of things back when I don't want them to talk to me, because I don't particularly like them (and I'm not sure why they have my number). maybe people say that to you because they find you annoying or something.

I hate when people text "hey" or "what are you doin???". -__-

They're busy getting laid. I suggest you move on from their flippant text and go do the same.