This drives me absolutely bonkers. Perhaps it was my upbringing -- my dad owned his company and was the face of it (sales, marketing and "doing"). Being late to a customer meeting is a sure-fire way to blow a first-impression. As a result, our family was on-time or early with rare exception.

I look at it this way - I have a busy schedule -- 4 kids, sole provider with a software development job that directly contributes to the revenue the company I work for receives and private developer of software that my customers enjoy. I even waited for a moment where I'm blocked to write this reply. If I schedule personal time with a friend or family member, it's being done at the expense of something else. I've decided that my time with that friend is more valuable than my core obligations. I value that time immensely and wouldn't want it reduced as a result of my tardiness. When the person/couple I'm meeting with chooses to be excessively late, I assume that they didn't really want to come at all and that they were simply being "nice" or fulfilling some sort of family obligation[1].

And it's not limited to friendships. I owned a gym membership and I'm an early riser (5:00 AM most days). The gym -- Bally's at the time -- opened up at 6:00 AM according to the sign and paperwork I agreed to when I signed up for a three-year commitment. In the first month, I showed up right at opening time only to find out that three out of the four days the opener arrived 30 minutes late. That's half of my workout on those days. As a result, I was receiving 2/3 of what I was paying for -- I'm directly paying for time to access a building and its equipment. The first month I prevented the automatic payment from processing and wrote a cheque for 2/3s of the bill along with a note explaining the situation[2]. This went over like a lead balloon. If I received 2/3 of what I ordered at a restaurant, I would have either had it resolved or left them with the bill after explaining to the manager.

[1] From the opinion of someone who values punctuality and my own time: Showing up late to an event because you feel obligated to appear there is far worse than saying "I can't make it" or even "I have more important things to do". I can respect that. There are certainly times when obligations related to a relationship can't be missed -- obligations you may or may not want to go to, but think about that for a few minutes. And what's wrong with saying "Well, that time is a little early and I have another obligation -- I'm OK with it, but could we push it a half-hour later?" If you don't want to go, why is that? Should you, perhaps, shed yourself of that relationship if devoting time to it is resulting in you wrecking it anyway due to your tardiness? Are you too passive to simply assert yourself with that person? Is there some way you could suggest to change that event to invoke the necessary willpower to show up somewhere near the time you're expected? Are you too selfish in thinking that your attendance is so important that you can just show up whenever you want -- despite everyone elses' schedules?

[2] I ended up successfully breaking the contract after filing a small claims action (that would have never been won).