Much as I agree, I think Freddo pointed out that they make too much money from PS2 compilation DLs to do that.
I honestly don't think putting the PS2 BC back in would really hurt compilation sales.
If there was no BC: people who still have the original games will already have their PS2. In other words, they would be less likely to buy the compilation anyway since they already have the games.
That said: the compilations are:
1) conveniently come on a single disc
2) updated to HD graphics
3) may include trophies/achievements (such as the GoW collection)
Thus, compilations might still be attractive to people who already have a PS2 and the PS2 games. It would even be attractive to people who might otherwise buy the PS2 games (if they don't already have them) to put in their PS3 because the PS2 games may be more difficult to find, especially if they are phased out (such as what Gamestop is currently doing to original XBox games). And think about the hard-to-find games for compilations, such as ICO for the upcoming SotC and ICO compilation.
If no BC: Even if Sony released all the PS2 as compilations, it would still be less expensive for me to buy a new PS2 than to purchase the compilations to re-create my library of oodles of PS2 games. Even if they were downloadable off PSN (and somehow only BC worked with the PSN titles), it'd be less expensive for me to buy a new PS2 than to purchase PSN PS2 games at non-competitive/realistic prices.
MS and Nintendo offer BC for their consoles, and their sales are still better than the PS3. In other words, the BC hasn't made the 360 or the Wii less competitive, it would seem.
So, from my thoughts and speculations, I would think that re-introducing BC wouldn't be disastrous or shooting their profits in the foot.