"Free for all" parking spaces allow you to trade your time (hunting a spot) for parking, the same way coupon-clipping trades time for a discount on food.
You can say "eliminate coupons, all food should be at market price", but coupons really are an effective way of helping people. They segment the market by being too time-consuming for wealthy people to bother with, and are a job for people who don't have a higher-paying one.