In very short words, the game has not finished its development cycle, and it's chance for SE to milk money from those nostalgic fans. Why sell it once when you can sell it 4 times ?
They are admitting that they have no idea why the PS4 is selling much better than PS3 in more than one occasion, kind of weird.
The way I see it, it's selling because of its brand name PS brand has been around for 20 years now, they didn't even change the name always has been Play Station, even my 75 years old gandma knows Sony's Play Station. Same thing could apply for Wii U but the marketing behind it failed miserably, and that's where Sony succeeded.
Non gaming enthusiasts and parents have no idea what DRM is or even watched 2013's E3, they go with what they know "brand name" that hasn't changed in 20 years, unlike Nintendo's consoles NES, SNES, Game Cube, Wii, Wii U. The same concept can be seen with Apple and their products, brand name and marketing that's all you need to sell your product.
just_Mishaari's comments