They don't bother doing more than a token effort at compacting because unless you have really crappy soil the foundation is likely strong enough to spread the l

They don't bother doing more than a token effort at compacting because unless you have really crappy soil the foundation is likely strong enough to spread the load to enough soil to bear the weight without cracking. If foundations didn't need to do that job they'd have a lot less if any rebar. Basically the way they do it is cheaper and good enough.