I wouldn't say I think backwards compatibility is mandatory (I believe the 360 excuse was also technological), but it is a nice thing to include. Especially with digital content being a major aspect of consoles, I absolutely want my old content to transfer over to my new system.
I bought a Vita partially because I never bought a PSP.
The Wii could play games from every single Nintendo home console, thanks to BC and Virtual Console. That is so rad and I want that to be the norm for every system. Even if I have to rebuy old games for a few bucks, I'd rather have less systems needed to play my games. My 3DS is loaded to the brim with Game Boy, Game Boy Color, NES, Game Gear, 3DS, eShop, and DSiWare games. It's the best system ever because of that. Oh yea, and it can play my DS games, too. <3 3DS.