The only real downside to switching out to non-runflats is the fact that if you have a tire failure you don't have a spare. You can get a little pump and sealant, which is how some of the new cars deal with that, but if there's catastrophic damage it won't help. However, that is also true of runflats, if something tears a chunk of sidewall out you still can't really drive on it.
Only perfect solution is to purchase a spare tire to keep in the vehicle, but that eats up cargo space and adds cost which not everyone is willing to do.
The general benefits of better ride/noise/tire life are so worth it though, run flat tires are just terrible compared to regular tires.