If you have a printed coupon, you might spot in the fine print the cash value of the coupon. This is usually a tiny amount, often as low as 1/100th of a cent. This is printed purely to tackle older laws that were originally created when trading stamps were first popularised in the 1890s. As they grew more popular, laws were enacted to protect a minimum value for the stamps, and those same laws still apply in some states. Coupons are therefore printed with a minimum value just to ensure they’re valid and legal in every state.
And yes, you can cash in your coupons legally, so if you happen to have one hundred coupons for the same store lying around your home that you don’t intend to use, you could cash them in for a cent – but you’d have to mail them in to do so…