1- lower level athletes. Being a half step slower than pro athletes means constant switching is creating wider gaps.
2- Longer shot clock. when you are switching as much as is required for peel and switch, those 6 extra seconds per possession equate to an additional switch per possession.
3- Shorter 3 point line. The shorter line means offense is initiated closer to the basket, so there is a smaller window for reaction time for the switch. This is compounded by the athleticism gap mentioned earlier as well.