Even on my Expensive L Primes, I use the Top of the line B&W MRC Nano XS-Pro UV filters. Its simply superb.
I don't use them much myself ... but I know many do and swear by it. Is this because you feel there is no perceptible change whatsoever in high-performing lenses or you have made your peace with the potential trade off for possible protection? And, I did say "potential" trade-off.
I want to protect my front element from cleaning, scratching, chemicals, abrasives, small meteorites from space or anything else from touching it. A UV filter already saved my 24L II once and will continue to use them.
I cannot distinguish IQ loss from the filter, B&ws are that good.