Theres also the 'I pirate to get a glimpse, if I like I'll buy' how many people realy do this, some do, but I doubt its many, they've already got the game, why delete it and go out and buy it if you've already got it? I doubt many people really do this.
I do this, depending on the game I'll either buy it for myself if it has online or for someone else if it doesn't. Sometimes both. For example I initially pirated the Ace Attorney games, bought 5 and vs. Layton when they came out, and bought two copies of the trilogy on 3DS and gifted one.