Although I personally think the JK's engine air intake is quite high up & pretty well tucked away up against the hood, some people have had issues with hydrolocking when fording deep water crossings, and many consider snorkles to be almost manditory.

Spare a thought for poor Toyota Prodo drivers; what were the designers thinking when they positioned the intake, & then making things worse by fitting the factory bullbar? Have a look at the link below (oh, if you're asking what a JK owner is doing looking at Landcruiser forums? A poster on another jeep forum was sick of everyone complaining that Jeeps were inferior in design & manufacture to Japanese SUV's, & suggested that members have a look at a few Toyota forums to see the truth. This was the first thing I came across)

I should add that this is a RHD vehicle; the model & factory bullbar may not be the same in the US...

http://www.lcool.org/technical/120_s...ingestion.html

 

I don't think they are mandatory at all. I have ridden through some pretty deep water with my cold air intake, which obviously severely increases my chances for hydro-lock. I drive smart and steady I haven't had any problems. If you plan on crossing deep water often, though, I'd definitely say its mandatory - otherwise just exercise some caution and you'll be fine...that's my working theory at least...