I don't but that's because a) I have a HUGE backlog of games b) I'd rather buy a game at full price* if the game is one that I have been looking forward to or I liked the developer's previous works c) I don't like buying bundles only for one or two games and then have keys that I cannot use.

(*Full price meaning something like 9.99 EUR, if it's something like 40 EUR....yeah no, I'll wait for a sale :D)