If I'm just going on a 20-ish mile ride out of my front door by myself and it's not critical I get anywhere in a timely fashion as I'm just looping back home, I don't bother as worst case I just walk home. My roommate also doesn't mind if I give him a ring if need be to get picked up,
When I take the bike to work, I definitely bring supplies to patch a flat as time is of the essence. I also have my backpack on me so it's easy to carry repair stuff.
When I do go on group rides, they're small, usually 4-5 of us, and we always make sure someone has a patch kit with them (usually my brother) and they're always happy to help anyone. Due to the small size of the group, if one person stops with an issue, we all stop to help fix it anyways, so it makes it unnecessary for each person to have a patch kit.
That being said, I've been meaning to get a small saddlebag to carry a patch kit for my rides but keep forgetting to get one.
Lastly, I'll stop for anyone if it looks like they're having issues, whether it's a cyclist, a car, motorcycle, tractor, I'll pick up hitch hikers in my car, whatever. I like helping people and don't judge on a lack of skills or tools to repair a problem. It has never even once crossed my mind to think less of someone just because they don't have a patch kit. Not everyone is going to have one and that's okay. If you have one, great, and be willing to share. Don't be stingy just because you forgot your 8 foot ladder to climb down off your high horse.