My partner is an amazing man. He's thoughtful, caring, smart, handsome, and a total horn dog... he just can't seem to get anywhere, ANYWHERE, on time. He chalks it up to gay culture and is quick to point out that most of the people we meet up with aren't the best about it and don't seem that bothered, but it's now gotten to the point where I have to tell him a different time to be ready in order to get him close to when we actually need to be somewhere. Am I missing something? Is there a gay culture lesson I missed? I had lateness shamed out of me by my German family, and it causes me no end of anxiety when we're going somewhere, and I know we're going to be the last to arrive.

What does the internet think? Is chronic lateness disrespectful, or do I just need to lighten up?

EDIT: I'm seeing a lot of "rude," "selfish," "disrespectful," "inconsiderate," and "asshole" in the comments. If I really thought he were any of those things on a consistent basis, I would have walked away from the relationship a long time ago. This is something he and I can work on together. I was mainly looking to see if I was being reasonable or not. What is disturbing is how many men here are clearly such masters of healthy, lasting relationships that they'd be willing to turf a man for being late when there are so many worse traits he could have.

EDIT 2: He has ADHD and was raised in the semi-rural south... for those who don't want to sort through comments.