Paging and PIC executables

I'm having a hard time understanding the need for PIC executables when virtual memory is being used. From what I gathered each program is assigned an entry in the page table and therefore has the illusion that it has the whole memory at its disposal while the paging mechanism takes care of possible relocations, pagefaults and so on.So if any program has the illusion of owning all possible memory addresses why would one use a PIC?