As for why roads are normally made out of “normal” concrete, it’s very expensive to build roads like that.

Pavements are cheaper to build out of concrete because they only carry the weight of pedestrians, not lots of rolling vehicles.

You need a pretty thick slab with rebar in it if you want to build a road surface from it, due to how weak cement concrete is under tension.

Maybe. OTOH the bays of bus-stops tend to be made of the rebared thick slabs in a town with higher traffic I happen to know. Since about a decade at least. Before that there were always ruts in the asphalt, so deep they needed to be fixed again and again. Not so with the rebared slabs.