It's more rude to expect that random people should kiss your ass for something you decided to do without any prompting. I can see that if they asked you to do it, then did not thank you, but that's not what happens. You opened the door, you non-verbally offered to hold the door for them, don't voluntarily do things that you don't have to if you want to try and hold the other person to some obligation to you. That is just being an ass. And personally, I like seeing their eyes light up a bit and getting a smile, more than if someone would say "thank you".
As a serious answer, I just hold a door open for a couple of seconds as I'm passing through, unless someone obviously needs help.