Wny does Sony not have a 5 million seller on PS3

[GameAnalyser]

it mite start doin 3-4 mn at a regular pace for most upcoming sequels...and probably even more. partly the initial low userbase is to be blamed..but MGS4 still being able to manage 4.3+ million already is a great and uncharted 2 is all set to cross 5 million eventually,