NASCAR had to do something to curtail the speeds they were seeing at the super speedways in the 70s and 80s. I still remember watching Bobby Allison hit 200+ mph at Talladega, getting airborne, the proceeding to take out half the safety fence on the front stretch. Also, NASCAR is not the only motorsport employing restrictor plates. DTM, F3, LMP, FIA GT, and more utilze them as well.
The problem is physics
. The restrictor plate does it's job; however, on tracks like Daytona, groups of cars together nearly eliminates the restrictions brought by restrictor plates because of how physics works. Combine that with the wind streams inside the "bowl" and you have a recipe for disaster.