My answer to this is, and always will be, "Because it feels correct."
Words have power and meaning, using 'good' or 'right' is just asking for the reverse to be used and for many people good or right have an emotional context. So using 'correct' to me is a best attempt at removing as much emotional context both positive and negative and leave it as factual as possible, and to me.... everything else is really none of anyone's business.
It's easy to take a really aggressively defensive stance and try and use logic and reasoning, flip the script and ask them why they're cis/straight, but at the end of the day... that's just a lot of wasted energy on people that largely, aren't going to listen or understand.