Will somebody please tell me why so many of these young men (and not-so-young men) are wearing loose, lightweight lower garments that look like skirts?

No, don't bother to try to tell me that what they have on their nether limbs are basketball shorts. I know a skirt when I see one. Just now a guy walked past me with his skirt down to his mid-calf, flaring out into a nice bell shape as the wind caught it. Good ankles, no socks, big humongous "athletic" shoes. So you say!

A woman would call that garment a split skirt or culottes or gauchos. Men call them shorts. How, if they go down to the achilles tendon, are they shorts? How do they keep them from falling down around their ankles?

They look ridiculous.