After all, the demo is supposed to highlight the good to get people to buy; putting out an unfinished demo (i.e. the game's not polished yet) wouldn't be a good idea.
but the best money is made with release and preorder sales.
if a game doesnt get enoug attention in front of the release, people will buy it used or wait till its gone budget.
so they just need to cut a piece out of the game , finish it fast, and demo it.
a demo weeks after release doesnt help much to hype a game.
and the bigger the hype the more they can sell fast.
