That severly shortens the lifetime of an LED, like by a factor of 10. So I would guess it is not common because much of the benefit that gets marketed is the longer lifetime. It is possible to build a better dimmer switch which actually works across the full profile of voltage variation but the problem then is you have to pay an engineer money and why do that when you can spend money on booze and dinners to win more sales contracts with your lighting distributors and get a higher ROI? The lighting world is a very consolidated place.