Counter-Strike is actually one of those instances where DRM adds value to a product for paying customers. Counter-Strike is a very popular target for cheaters using client hacks like like aimbots and transparent wall hacks, and one of the ways to avoid those players is by hiding behind a pay wall. Every time a cheater is caught and banned, the only way for them to get back in is by paying $10 to re-buy the game. Adding DRM to the client ensures that this pay wall remains intact, meaning that cheaters can ruin my multiplayer experience constantly only if they are willing to inject a fair amount of cash into the system (and very few are).