I didn't say anything of the sort. In fact, I said the opposite: I specifically imputed good faith to both sides and called it a disagreement. The departed principal believes their work to have been instrumental; the remaining team believes otherwise. Without vesting, the lone departed can kill the deal.

The "10 years later" example was not made up. Like I said, I've been a party to a "didn't think we needed vesting" scenario, and it's a mistake I won't make again.

I 100% believe you successfully managed a company that was built on handshakes. Like I said, you got lucky (if you'd prefer the alternate framing, say instead "we didn't get unlucky"). I have trouble understanding why you'd leave something like this up to chance; companies are (in most cases) many years worth of dedicated enterprise from multiple people, and deserve a few hours of de-risking by spelling the arrangement amongst principles out in writing.

I'm hardly alone in the belief that founders should vest; you yourself called it a "default"; I quoted Spolsky on it below; and it is, all else aside, certainly a norm in the US. I'm still waiting to hear why you wouldn't do this. Because it helps investors "steal the company" from you? If you raise VC, this debate is especially irrelevant, because while I believe you took funding for one or both of the companies you sold (as I believe all the experiences you relate), I do not believe you could today raise a round from an actual VC firm without taking on a vesting schedule.