Optimistic locking works great when what is excluded is effectively a calculation. The annoyance, though, is you have basically acknowledged that you can use a compare-and-swap at the end of your calculation to know that things worked.

This is not at all always the case, though. Sometimes, what you need to use mutual exclusion for is actively working with something that is, itself, active work. That is, sometimes you have to stop something even starting.

Think about how you would model a laundry mat. It isn't enough to say you could use optimistic locks for access to the machines. You can't use the machine until you can use the machine.

This is not unheard of in computing, either. Sometimes, you can't process a buffer until you know it has been finished by the code before you.