I suspect pump petrol for the last 20 or so years has been much, much cleaner than in the past. I did a service on my dads 98 5 series a couple of years ago, it still had the factory fuel filter on dated 07/98. Cut it open with some snips after leaving it for a few days to dry out and, honestly, it still looked pretty clean. My 2004 Z4 doesn't even have a factory fit inline filter, the only filter BMW used is the one in the tank.