Well yeah but can you name a vehicle built for off road including any domestic pickup truck that doesn't have issues with rust. Fenders, rockers, frames etc. If you play in the mud and salt you need to maintain them. UTVs are no different. Ask yourself why Polaris would put the air filter canister intake in the rear wheel well so it is sucking in the air from the dustiest area they could possibly draw it from resulting in a 4k bill when the motor grenades.
Jeeps are fun, used ones can be had at a reasonable price but by their nature you need to be careful when you purchase because if the previous owner drove them the way they were marketed then they may have some issues.
But the aftermarket has an amazing amount of mods,upgrades and accessories to make your Jeep into anything you want and because the generally go 10 years between major design changes there are a large number of parts available if you need them.
Well, one of the advantages to owning a Jeep is there are always plenty of Jeep owners out there looking for parts, so if you get ahold of one with a bad frame, you could always part it out and sell the parts to another Jeep owner who believes they have a good frame....
I am saying if you go mudding or off-roading you will plug any of the drain holes they could put in there anyway. Not much different from the weep holes they put in the rear fenderwells and rockers of trucks.
I suppose it may have benefit to those who stay on pavement.
They put holes in the sides of the frame, so salt and mud could get in, but no holes in the bottom so they could drain, so not sure if that was planned, or just p*ss poor engineering. They probably didn't really care as long as they outlasted the warranty period.