Why is the ELF execution entry point virtual address of the form 0x80xxxxx and not zero 0x0?

Question

When executed, program will start running from virtual address 0x80482c0. This address doesn't point to our main() procedure, but to a procedure named _start which is created by the linker.

My Google research so far just led me to some (vague) historical speculations like this:

There is folklore that 0x08048000 once was STACK_TOP (that is, the stack grew downwards from near 0x08048000 towards 0) on a port of *NIX to i386 that was promulgated by a group from Santa Cruz, California. This was when 128MB of RAM was expensive, and 4GB of RAM was unthinkable.

Can anyone confirm/deny this?