Memory, I was around in those days and had some discussions on usenet with some of the guys at Sun regarding java (long before usenet turned to complete crap).
e.g. stack based variable handling, which on a modern machine makes it run slower, was faster back then because RAM was more constrained, so implimenting the equivelant of a paging system for the VM was thrown out, because the paging routines themselves consumed processor cycles. While this could be fixed with a rewrite of the VM, that isnt likely to happen, and it may break existing code that depends on such behaviors.