It's another take on game bundles, something we really used to love long time ago.

We would get a bunch of games at low price, but of course, you wouldn't want to play every game in the bundle. So people started trading unneeded keys between them and resale key sites popped up. This made developers less interested in bundling games, as it would eat into their sales.

So, we need to square that circle, how do we get cheap games and the developers still get paid. Digiphile's idea is to not give you the Steam keys, so you can't trade/sell them. But if you already own the game on Steam, you can trade it into credits which you can exchange for games from previous bundles.