Originally Posted by
ThermionicScott
Because the primary goal is, and always was, foot retention -- keeping the feet on the pedals when spinning fast or sprinting/climbing out of the saddle. That's why they're important for fixed-gear riders as well -- oftentimes, the feet are handling braking duties, so it's critical that they never leave the pedals.
- Scott
Having your foot leave the pedal when the cranks are spinning at 140 rpm plus can be pretty ugly... having solid retention is key.