I don't always say goodnight back, because if I'm sleepy I want to go to sleep then not wait till the person is done saying goodnight, then you text goodnight, then they're like sweet dreams, and you say that back too, then they're like don't let the bed bugs bite, and then you make a face and say GOODNIGHT! if you're in a relationship, however you definitely say it back, with your talkative friends who look for any reason to talk, no.
It is not only normal, but reasonable as well to expect a "goodnight" back when you wish someone a good night. It is more like when you say "hello" to someone; you instinctively expect to hear "hello" back.
It'd be nice, but no, I don't expect it because some people aren't used to saying goodnight, or sweet dreams and all that type of stuff, just like when you say Hi to someone and they don't say it back, lol. You expect it but it doesn't always happen
People can be so rude and it annoys me when they do not respond to good nite, hello, etc. some people have absolutely no manners whatsoever. I was raised to respond when spoken to. Verbally or written questions deserve a polite response.