I'm sure they have ligit function: deep water crossings and getting the intake above some level of dust... but I suspect their main deal is to look cool and indicate the status of their driver as an Overlander. Kind of a cliché which our rig already screams with all the other bolted-on accessories.
Don't ever intend to cross any water deep enough for the snorkel to be necessary, but we do, of course, get into the dust. Given that there is no removing the thing considering the rather large hole it was leave in the fender I might as well maximize its dust function.
All this to ask:
Would it be worth the trouble of installing a pre filter on top of the snorkel?