It's not just the power and capabilities, you also need to license IP (for example, IBM owns the Cell processor from the PS3). In any case, from Sony's point of view it's all about selling new hardware and new games, and you have to see backward compatibility in that light.

So, if you want to play PS2, you are a Retro gamer, and you'll be one Ebay. Or you'll be buying your games one at a time through some equivalent of the Virtual Console App Store. Retro collecting is a pretty cool hobby anyway...