We do in some places. Where I live (Iowa) we don't - but most people take better care of their car than that so it is pointless. As a kid I remember parts of MN requiring inspection and a few years latter dropping it when they realized nearly every car was passing so there was no point (this was emissions only not safety). In Texas there are regular inspections - but if you go to border towns you see a lot of those poorly maintained cars on the road (despite the inspection) and so people see more need for them and they keep them.