It’s a cultural thing and a learned one. I will say that because I was one!
I was one who would show up late to things and not offer explanations. I would certainly apologize for it but it was a routine occurrence. I got it from my mom.
After I married my wife she set me straight about the whole thing. I was late on her a few times and it bothered her a lot. Nowadays I am early for things, for the most part and it does feel a lot better.
It’s a lesson that people learn and if it bothers them enough that something that is late ends on time they will get the hint that starting on time will give them the full time to use. Sadly though many people don’t get that and don’t care enough to change.
RE: Late Arrivals and Lost Time: My Thoughts on Punctuality