Mostly cause it's become the best alt-SHA256 coin*, so a lot of the miners who couldn't make a profit on bitcoin anymore have switched to PPCoin.
This includes miners with some ASIC's too as the butterfly labs Jalapeno(for example) isn't really profitable on bitcoin anymore, but ppc is another story. I think this might help increase prices as the more people who hold ppc, the more acceptable it becomes as a form of currency.
*(look at the alternatives Namecoin for example has had a huge bug, and is merge mined with btc anyway)
Thanks. I know, I've had a lot of Namecoins and I think NMC is the best altcoin. Do you think that the bug of Namecoin will be patched in future?