The NTIA (U.S. Government agency in charge of the coupon program) probably didn't consider that the 90 day expiration date would be an issue in the first place, but since there are almost 50% of the coupons expiring before use...It's a huge oversight.
Even if Congress eliminated the expiration date on the $40 coupon cards, they would still have to print new cards for expired coupon holders. The reasoning? Once your old coupon card expired, the funds were immediately returned to the NTIA converter box coupon program, and used to fund other
DTV coupon applicants cards. Refunding the old expired cards would be a huge accounting debit and credit mess.