The reason Steam has survived and doing well is because it is updated and it evolves to meet the current climate. Remember when it first started? The system was designed for distributing Half-Life and official mods with a ropey Friends feature and some parlor games to play whilst waiting for rounds between CS. Then someone said "Why not get other companies on board?"
Now it is the biggest digital distribution service with the Steam Community added to meet the new social networking climate, non-games for sale, graphics drivers, adaptations for F2P plus Steam Wallet to support that new revenue model...it's come a long long way from playing Checkers as you wait for two AWP campers to kill each other assuming Friends was even working.
Shame the parlor games never came back though.