they're just so uncomfortable. you've got that bit that sticks between your big toe and just rubs. Why would you want to stick anything between your toes?
Then that's constant flap/wack flap/wack flap/wack noise they make. If the pain in between your toes wasn't enough to remind you you're wearing flip flops, then the blasted noise certainly will. Flap/wack flap/wack flap/wack...
Finally, the sole, designed to ensure that whatever you step on, the pain is sharply and directly conveyed straight to the base of your foot.
Hateful, hateful things
