Timing the start of something is not a simple process. Punishing people for being late disproportionately impacts poor and disabled people. Not all of us can drive a car or even have a car to drive. We might have to wait on other people, or use public transportation, and the more steps we add to the process the more likely something is to go wrong. Punishing people for being late is systematic oppression towards these groups. This punishment can include starting without people, especially if that itself is framed as a punishment.
“Let the late ones be late and miss out (they can read the minutes), and reward the prompt ones by not wasting their time” From the rusty's rules of order, something the IWW uses to organize. They are ableist.
On the other hand, waiting too long to start can impact people with limited time or energy. Not everyone can stay awake an extra hour just to wait for something to start.
This means that there is not one singular solution for how to start things (although obviously don’t do punishment). In small groups the best solution is to talk things over with everyone and get an idea for what everyone wants to happen, what can go wrong, and plans to mitigate any potential issues. If public transportation is running late, maybe someone with a car can go pick you up.
For large groups, most things do not need a strict starting time. If it is a large group and it requires strict attendance then you brought hierarchy into it long ago and ableism and such was always the conclusion you were going to get anyways.
edit:
organizing in a way where disabled people are inherently accommodated instead of shoved into some “extra” system makes a big difference
to reply to those below, it is "entitled" to think that it isn’t ableist to force people into systems instead of building systems around the people there.
to put it simply, if a group is organized in a way where you must actively decide to favor one social group over another systematically and it is always the same group, you failed and are just doing hierarchy, in this case on the basis of ability. It doesn't matter if you can't imagine organizing without ableism, that is still ableism.
I got a discord linked in my bio for people who are a fan of that form of organizing, as you can see here it isn't common even in these spaces
OP is absolutely mistaken that it's somehow ableist to stick to a meeting deadline or similar "punishment" for lateness, and t3rmit3 has said why much more eloquently than I could. However, you've said something that I can't let pass without a rebuttal.
This is making a moral judgment on what you believe is in someone's mind, and your judgment is based on a false premise. There exists an extremely common mental disorder (so common that some might consider it a form of neurodivergence) that when left untreated makes it much harder to do the things you want and are obligated to do. It's harder to start doing things, it's harder to stop, it's harder to focus yet too easy to focus, it's harder to remember important things, and it's harder to motivate yourself to do anything you aren't doing at any given moment, and anything you have to put effort into motivating yourself to do leaves you with less mental energy to do anything else in that category.
The one thing that can usually overcome all of these mental blocks is panic - when you're actually out of time and Consequences are approaching if you don't do something RIGHT NOW then you can finally do what you need to do and get something done - later than you wanted, worse than you wanted, more mentally drained, and with plenty of reasons to beat yourself up over it, not that it helps if you do. This is the reason behind why most people show up perpetually late. They might not let the emotional turmoil show, but if they're consistently a few minutes late for everything, I can just about promise it's not because they don't care.
People who have this disorder and receive prescription medication for it often describe the first dose as like receiving superpowers. The idea that they can decide they want to do something, and then just go do it? Without thinking about it? No buildup? No psyching yourself into it? No roundabout coping strategies? No reorganizing the entire structure of your life to make it happen? No bargaining with the goddamn monkey in your brain that almost never lets you do the rational thing? Wait, normal people don't have the monkey? They live like this every day, without any expensive pills? Impossible. It couldn't be that simple. Do they have any idea how lucky they are?
Your misplaced sense of moral superiority is unfortunately quite common, but it's not going to help these people, it's going to hurt them. If it's affecting their life, and it often is, they need treatment and training in how their brain works, not to be told they're a piece of shit who doesn't care about others and are choosing to inconvenience everyone else in their life including themselves. That's only going to put them in a worse place.
This is identical to "drug addicts choose to be drug addicts and so do not deserve medical care" except it's closer to "blind people choose to be blind"