Obviously if someone is literally right behind you, fair enough, it doesn't cost you anything to hold the door for half a second.
But when someone's about 100 yards ahead, they hold the door, they get split off from their party, you have to walk faster to recieve said door because you don't want to put said person out they have to walk faster to catch up with their party, etc.
I have mobility issues that aren't immediately apparent and the amount of rude comments or bitchy looks I've gotten because I physically can't walk any faster to get to the door, just let the fucking thing close! I can open it again.
Not to mention that you then have to say thank you, not a big deal for most people, but I don't like talking to strangers. I have social communication issues and I know I'll come off as rude or ungrateful when I don't mean to.