Purpose of crawlspace ?
A slab can be better for radiant heat in slab. Some places concrete finishers are hard to find. Some places require deeper footings, Some people prefer the comfort of a wood framed floor. Cost can enter the mix.
We both live in western chicago suburbs, in towns 20 miles apart. Both neighborhoods have trilevels, and ranch style homes primarily. My house was built in 1976 and his late 1960's. All homes in his subdivision have crawl spaces, mine slabs. The crawl space is creepy to me, there are animals in there. The slab seems so much ... nicer. Thanks, Joan