Well, I drew the marriage comparison up above but I guess I can belabor the point. If you told me that I can join a labor union but never change my job, I would not do so. If you told me I could join this awesome book club, but could never leave, I would hum "Hotel California" under my breath as I walked off. If I was offered a candy bar and told how amazing it was and it also came with a contract that this was the only kind of candy bar I could ever have, I would not buy that candy bar no matter how dazzling it appeared. If a gas station told me I could join their loyalty program but also forever after only had to get gas at their chain, I wouldn't join that, either.

Vendor lock-in: I avoid it in technology if it can be helped and it seems like a good principle elsewhere. Sometimes things just don't work out.

USSR had this possibility on paper and even offered a mechanism for exit (a local referendum). In fact it was dissolved after all republics including Russia left it. Probably the reason it was a mostly peaceful process with few exceptions.

True.

The Brexit went rather smoothly, if seen in historical context.