Plenty of minivans also have tall hoods. I assume by combi you're talking about a station wagon, and in that case you're trading cargo capacity and the ability to tow boats / trailers / campers / etc... Ego has nothing to do with it - utility does. You can fit more people and things in a larger vehicle, this isn't rocket science.
Which ones? Caravan's, Sienna's, etc all have significantly lower hood heights than a typical 3 row SUV.
They all have sloping hoods. A sloping hood increases visibility and reduces air resistance.
Why does a Kenworth have a sloping hood but F-150's and SUV's don't?
I don't think the cargo capacity argument really holds water. I drive a Volvo V60 wagon which has trunk space of 23.2 cubic feet. When it was in the shop, I had a loaner XC60, and I could noticeably feel that the trunk space was about the same, despite the vehicle sitting considerably taller.
Sure enough, the XC60 crossover has a trunk space of 22.4 cubic feet.
It's the same trunk, just higher off the ground, which to me makes it less useful to me: more lifting to get stuff in, harder to rummage through items (eg camping pantry), much more difficult to access my roof box.