because many/most/all fuel pumps are meant to have liquid resistance and burn up without it.
The fuel in the tank cools the pump, it's not necessarily because of the fluid resistance.
The reason you don't rev an engine without a load is because it revs and drops rpm's way faster than it was designed. The load forces the engine to accelerate/decelorate slower. So it's more like a sudden acceleration and stopping causing the added stress.
I'm also sure there is also an issue with oil and coolant not being able to lubricate/cool critical engine components fast enough to keep up with the unloaded revving.
2011 3.7L MT82 Kona Blue GT/CS Pedestal Spoiler, Cervini's HE hood, Stillen chin spoiler, BBK headers, GT T/B, Steeda tune, Ram 9.5 Dual Disc clutch, 3.15 axle T2R Torsen, 285/35/18 w/ Steeda 18"x 9.5"+44mm Q1s, Steeda Sports springs/Koni struts/Viking shocks, Shelby adj front sway bar, Boss302 Rear sway bar, Whiteline Watts Link, 14" "Brembo-ish" brakes and 3/4" front wheel spacers/ARP studs.