Steam is successful not because piracy is illegal. It is successful because it made buying games more convenient than pirating it. It is far easier to click, pay, get content than torrenting stuff and finding correct cracks/keygens, etc.
I have bought a great deal of games I played in 1990s (pirated, of course - there simply did not exist a way to buy games legally in Russia at that time), just because I liked them back then.
Also, please stop calling copyright infringement 'piracy'. Piracy is a dangerous penal crime involving violence and an open theft of possessions. It has nothing to do with copying information.
I have bought a great deal of games I played in 1990s (pirated, of course - there simply did not exist a way to buy games legally in Russia at that time), just because I liked them back then.
Also, please stop calling copyright infringement 'piracy'. Piracy is a dangerous penal crime involving violence and an open theft of possessions. It has nothing to do with copying information.