I disagree, PS2 playback is needed since many people have a ton of PS2 games they still enjoy playing. I'm pretty annoyed with the next gen consoles and how they didn't offer proper backwards compatibility when it was promised. The 360's is rather half-assed with only a select group of first party games being offered an the PS3 just dropped it altogether.
And I think it's daft to say if you want to play PS2 game just buy a PS2, you already purchased an expensive system, it should play back games just fine. I really think it's all a ploy to get people to buy the games again from the PSN store or from Live for the 360.