Soon after experimenting with the LBP2 beta, something became apparent to me: the tools in LBP2 were much more powerful than anything LBP1 could have. Not simply the logic gates and microchips, but things like movers, destroyers, anti-gravity, movie cameras, bounce pads, sackbots, etc. All of these things could be made in LBP1, but their implementation would take a significant amount of time and thermo compared to what we have in LBP2. That's when I realized that most LBP1 levels had been taken down a peg right off the bat, because there was so much more we could do now, faster and more efficiently.
My theory is this: after any serious creators started releasing new levels, it would trump any (or at least most) of their previous work by a landslide, without having even fully mastered the tools yet. After a few more months, they become more comfortable with the tools, learn new tricks, and make even better levels. At that point, why would anyone go back to LBP1 levels other than out of nostalgia or curiosity?
That's the inherent flaw I see in backwards compatibility: it's only useful as a transition from the old to the new. Once that transition is complete, the use for backwards compatibility drops significantly. But did we really need that transition?
My opinion is that LBP1 started with a clean slate, and got to have many amazing levels that just kept getting better and better over time. LBP PSP started with a clean slate, and the same thing happened. LBP2 would have been no different if it hadn't had LBP1 levels to play (some creators and players might have been miffed in the first few weeks, but honestly, who would have held out on LBP2 just for that reason?). Whether any of the tools/bugs/story levels would have been improved as a result is anyone's guess though.
I've locked pretty much all of my LBP1 levels from LBP2 because of BC issues. I sometimes feel like unlocking SackMech levels, but then I think: why bother unlocking an LBP1 level when I could upgrade it in LBP2 to be even better? Quickly followed by: if I'm going to upgrade an LBP1 level, why not just make an entirely new level that makes good use of the new tools? I guess what I'm saying is that LBP1 level compatibility really doesn't seem all that useful to me now.