Convenience and (the perception) of safety, both from law and malware. Paying a reasonable amount for a movie that is easy to find and watch is a no-brainer for me. Of course, my time to income ratio is low.
People don't buy bottled water for the bottles, otherwise they'd throw away the water, and keep the bottles. Instead they keep/use the water and throw away the bottles. The water is what they pay money for, you can get that for free at home.
OK, I'm sure there are counter-examples to just about ever rule. However I think it's accurate to say that the vast majority of the population buy bottled water for the water, not the bottles. My point stands.
Free water from home tastes worse. Making the analogy, if they want to sell content they need to give extra quality than "illegal" download. Cinema large screens, live concerts, etc. I cannot see another way.
I'd pay 5-10 bucks for a high-quality mp4 or mkv, even if the site's interface was terrible. Right now I rent movies, about once a year. I find myself wanting to buy them online once or twice a month.
Because you want to support the making of more movies of the same kind. Because you have a conscience. That said, there will always be those who shoplift in stores, or pirate movies. I don't believe those people constitute the majority of the population.
Because you want to support those who produce the content, if you like using it. Not supporting them while using their creation is sheer disrespect, regardless whether piracy is illegal or not.
I don't think it will. We'll try to maintain it up by any means possible as long as there's a satisfying worldwide alternative to buy/license this content.
In a way, it's a political stand. We're already in contact who could help us make an alternative that would be both legal and ethical.