You are wrong about the wood. Wood 2x4's are commonly used
to fill expansion joints in new concrete driveways. The
main problem is shrinkage and warpage of the wood. You
don't see crushed wood and you don't see spalling caused by
the pressure

Just because someone uses a hammer to drive a scew doesn't make a good practice.
I see evidence of improper installations and poor workmanship all the time, but
it doesn't matter how many times something is botched up or the number of people
doing it--it is still shoddy practice. The fact that you don't see evidence of
damage merely means that in the cases you have observed either the temperature
range is not very extreme or the slab is free to move on the opposite end. And
unless pressure treated wood is used the termites would make quick work of it,
at least in my area they would.

Regards,

John