It's been like that since the end of Prohibition. Only state stores (Wine and Spirits Shoppes) can sell wine and hard liquor. It was basically done to keep shit under control, but has turned into a patronage system and cash cow.
The chances of getting rid of it are slim at best. Part of the problem is the fact that union workers work in the shops. They refuse to go down without a fight. Another problem is that the revenue has been helping out the budget during the current fiscal crisis. (Although some have argued that selling it off could be a bigger windfall...I agree.)
The other problem is the very nature of PA. Philadelphia in the east, Pittsburgh in the west, Alabama in the middle (to borrow from James Carville). A lot of groups were against Sunday sales (which started at select stores a few months ago) and don't want these items to be more available. It's also incredibly hard to get a liquor license in this state (though it was made a bit easier a year ago)...a license on the market could fetch $2 million easily, and you'll find many places that are BYOB. The state will only issue permits for every so many number of people. Based on the current population, there are currently "too many" permits out there, so no new ones are issued (at least as of a year ago).
The Pennsylvania Liquor Control Board is my main pet peeve about living in PA. It's obviously something I can deal with, since I'm not an alcoholic.
But why make it so fucking difficult and expensive for residents to partake in a spirit?