> Aesthetically, we want a clean, graceful line from hip to ankle even while holding things.
How are side bulges above the knee clean and graceful?
> Where is there enough support to prevent items swinging around uncomfortably?
Because pants are looser around the knee than the waist, heavy items like a phone will constantly be swinging around uncomfortably down there -- same as they do in cargo pants.
As for the problem that started it all:
> Putting a modern slab phone, a wallet, and keys into a pair of skinny jeans will leave even the most fashionable figure looking looking like they’re wearing batman’s utility belt as underwear.
A little bit, yes, but it's really just the least bad solution. Everything else is even worse. The market has settled on pockets as they are, because they actually truly work best.