> 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.

You can have a "pocket-in-pocket" to avoid that problem. My Lululemon trousers [1] have that where I can fit an iPhone 8 so it stays put (I don't store my iPhone as the "double-pocket" in the pictures, it is rather a hidden pocket inside the pocket on the right hand side)

[1] https://www.eu.lululemon.com/en-lu/p/commission-pant-classic...