I've talked to many people about why exactly do they download software and games and music illegally? You would be surprised of some answers I have received. Sure some people just want to download everything illegally even if they can pay for it. Sometimes you just don't have the money to spend and pirating is an accessible platform.
One popular reason for Software pirating is that most jobs require experience with a certain application, thus making a catch 22 of "well that software is expensive, I cant buy it how am i supposed to learn it?" So they download it to learn it and then they ideally can get a job in the industry.
Music pirating today is a bit different, sometimes people just want a digital copy of the cd, if they dont offer one and ripping a cd to a pc is frowned upon or blocked most of the time. When the cd/dvd gets scratched the thought is "I need to repurchase the cd/dvd just because I hit a bump and its scratched" The industry wont let you make a "backup" to protect your investment most people wont bother they will just download it at that point. They figure they paid for it once why should they pay again.
Originally with P2P software it was more typically seen that people used to just downloaded popular songs because it would take a few hours to download just one song and an entire albums could take a week. Now one could download an entire artists discography in just a few hours. The industry is smarting up in the past few years, most of the time they offer a digital download with music and movies.
Games are expensive and some families just cant afford them, so either they don't play it until the cost lowers and risk it not being popular or pirate it and take the risk of getting caught.
Until companies offered digital downloads bootlegging music was the only way to get music to a Mp3 player or to burn music cds and make custom mixtapes.