That is surprisingly bad. My substantially larger Ram 3500 dually gets 15mpg even when loaded with 4000lb of cargo in the bed. Towing a trailer I get about 14mpg, unless there is a substantial headwind (since the trailer is much taller than the truck), that is the only scenario where it drops to near 12mpg.
The example you gave is the Ford F150 Raptor which is an enthusiast model for off roading that is extra inefficient and I wouldn’t call the Jeep Wrangler a “big SUV” but it is an incredibly fuel inefficient one with terrible aerodynamics.
[1]: https://www.fueleconomy.gov/feg/noframes/50104.shtml