My day job is construction. In the Union carpenter world if you aren't early you are late. Late people get laid off. Once you get the mindset it's hard to deal with tardy people.
That said, I show up to practice on time, fire up my gear, run the drum machine up through the PA and start playing. By the time everybody else is ready to play, usually half an hour later, I'm warmed up and grooving. I pick a song we need to work on and get it going, they can come in anytime. If the PA is still broke down from the last gig I start setting it up.
Tonight, I figure the PA is sitting where it got dumped out of the truck Saturday morning. I plan on getting there 20 minutes early to get a few things up to the studio and run cables. I'll get some help, and we'll get it done.
Practice is from 6-9. Once a week. At 8:55 I say one more song, and at nine I'm on the way out. I'm not bitter about it, just doing what we agreed to. When the idea of an "extra practice" comes up, I tell them that I'm busy, and the extra practice wouldn't be needed if we didn't waste two hours a month at regular practices.
Sure, they could do better, but on the whole it's a minor thing. If I wind myself up about it, I'm not likely to enjoy the evening's work.
I have fired guys who are consistently late, but they usually come with other problems as well.