Actually, the problem is deeper than just that. It's not just a lack of incentive - it's counter-incentive. The phone companies are using the OS version to segment their market (high-rollers get a 2.1 device like an Incredible, cheapskates get a 1.5 device like an Eris or a Tattoo). The phone companies don't want you to be able to cheat their pricing by upgrading your Eris to 2.1. Given how obsequious and accommodating the handset makers are (they have to be - their sales channel belongs to the phone companies and they effectively have to do all of their marketing to phone company execs rather than us), it's unlikely that they'll do extra work to piss the phone companies off.