In short: We (as a field) tried them for many many (many!) years now and they have been found lacking -- in practice they're just too hard to get right for larg

In short: We (as a field) tried them for many many (many!) years now and they have been found lacking -- in practice they're just too hard to get right for large-scale systems. EDIT: The mutexes themselves are easy enough to get right, it's the systems using mutexes that are too hard to get right.