Prosites Coupon Suggestion

I really like the idea of the coupons in Prosites. However, I don't get why we need to have a specific start date. Most promo codes I know of start when first used, whether it's today, next week or next month. For instance, they get 50% off for 60 days when they use it, starting from the day they sign up.

Maybe I'm just reading it wrong.