Not that I ever pirated anything in my life, but if I allegedly had, I would have stopped when I realized how much value Valve’s Steam service provides for gaming.
The overlay, offering access to a webkit browser, a clock, and voice or text chat with people you know on Steam, almost completely removes the need to switch windows from the game you are playing.
The ability to access all of the games I ever purchased through Steam on any computer (granted only one computer at a time) which is able to run them alone makes it worth buying a game from Steam over having a hard copy or from some other service (many of which will have a really hard time building up brand loyalty, something even Steam struggled with in the beginning *cough*Origin*cough*).
Steam also keeps all of your games updated automagically. I often don’t even know they are being updated until I get back onto Steam (which runs in the background all the time, taking up less resources than an Explorer window when idling) and see that something new is finished.
On top of all that, Steam’s constant sales make me feel like a kid in a candy store every day.