I think you got lucky. That's great, and I'm happy for you. We could bicker about the odds. Maybe it's 60/40 in favor of you getting away without vesting? Maybe even 70/30? The first company I ever worked for, which also had a successful exit, didn't do vesting. It never occurred to any of us to be ruthless about it, and it happened that nobody left early anyways: they had gotten the team exactly right. Vesting wouldn't have made a difference. Maybe that's you, too?
Me, I've been working for small companies ("startups") since 1995. I've been on the founding teams of 5 of them. In all but 1 of them, key members of the team left at some point. In each of those situations, lack of vesting would have meant they left with a full share of the company, leaving everyone else on the team to work --- possibly for years --- for that person's equity. In one case, that's exactly what happened, only we didn't know it until the end.
That's a mistake I will never make again.
These are, I think, the very worst kinds of mistakes startup founders can make. The kind that don't really impact the company on a day-to-day basis and that you won't notice, until you're actually successful and finally at or near accounting for that success, and you realize you did something stupid that tolls the whole fucking enterprise. You might not be able to do anything to mitigate, you can't even bail from the company and do something different, you're never getting the time back, the damage is done. Vesting isn't the only mistake like this, and it's not the worst, but it's bad.
And for what? Does it somehow make you feel better not to vest? I don't get it.
(I don't pretend to understand Alex's logic about vesting as a solo founder but did not think hard about it either).