[old_tv_nut]

Since the spatial resolution of 480i and 480p are the same, it is likely the industry decided not to make the distinction in order to avoid legal and regulatory challenges. Accepting 480p does not necessarily mean it has the capability to convert 480i to 480p. Displaying 480i as 480i is better than doing a poor, cheap conversion job; that is probably why conversion is not included. On the other hand, conversion of 480p to 480i is very simple and cheap.