It's an attempt by PayPal to get you or any user to keep more money "on account" there, tied in with something novel like Bitcoin. The more money you have on account the more likely you are to use it to pay for things using their service (for which they can charge fees)...even more so if that money on account has gone up because it was tagged to some Bitcoin-pegged investment.

I haven't seen any of PayPal's marketing or PR on this...is it a bait and switch? Did they promise to be able to buy bitcoin specifically?