Comment by astrobe_

I've always believed that they kept 32 bits ints on 64 bits CPU as a default because going full 64 bits would make the code and data structures bigger for "no reason" (it's not often that one hits the 4.10^9 limit in system code (if you don't count timestamps, that is)). For instance, a load-register-with-immediate instruction would normally take 5 bytes (opcode+value) on 32 bits, but 9 bytes on 64.