Ben wrote:

Since I am operating on a smaller budget, I was wondering what reasons
are there why a sheet of plywwod - 3/4" or 1" oak or birch supported by
doug. fir (4x) lumber would not be used?

Because it's too thin. Laminate two sheets of 3/4" ply together and
then you're talking. Cheap spruce shuttering ply is the best deal.
Stick some 4mm MDF over it with double-sided tape, wax polish the top
and you have a couple of years' life replaceable top to take all the
chisel slips.

This is regularly discussed - seach the archives.