There were plenty of times where I wanted a copyrighted product (movie, song or app) and decided pirate it instead of buy it because it was more convenient. Had it been difficult to find said copyright material online, I would have gone out to the store to buy it. In these circumstances the sales were lost because it was a hassle for me to drive to the store to buy the product.
Going to the store consists of having to get dressed, fight traffic to drive to mall, find parking in a crowded parking lot, walk to the store, find the product on the shelves, stand in line to pay for it, walk back to my car, and fight traffic on the drive home, -a process that takes several hours. Instead, in that same amount of time, I can torrent it and spend the time doing something else, fun like watch TV or play a game, or get some work done. To me, that's a no-brainer more efficient use of my time.
Also, why would I pay for a product when there is an easily obtainable copy available for free? Sure, I'd like to support the artists and developers, but I have to watch out for my own pocketbook too. This may make me a sleazebag, but that's just the way I am. Not gonna get much sympathy from me if it means separating me from my hard earned cash. If the pirating option was not available to me, I'd be a paying customer, and the RIAA realizes that this is true for a lot of people as well, which is why they're fighting so hard with underhanded tactics.