There are many reasons why Sony could have cancelled backwards compatibility, but none are verified.
Download [PS2 System Data] from (Play Station®Store). When the download completes, [PS2 System Data] will automatically be installed.
[PS2 System Data] is saved in (Game Data Utility) under (Game).
When you start a Play Station®2 format software title that can be installed in the system storage of the PS3™ system, the following screen is displayed.
One of the most annoying things about the Play Station 3 is its lack of backward compatibility on some models.
There are several hacks out there to do this, but most of them involve extra hardware, like the Cobra-USB Dongle, or downgrading, which can cause all sorts of problems.
If you have a modded PS3, you can use it to play any PS2 game, even if your model doesn't normally support it.