Lack of respect for a law.
People have no respect for copyright law any more. Or a lot of other laws too, but let's focus on copyright. Why is this the case, and what can be done to fix it?
Firstly, people won't respect any law that they see being violated with great frequency and little risk of enforcement action. But copyright is practically impossible to enforce online - this has been the case ever since the introduction and immediate explosive growth of Napster.
Secondly, people won't respect a law that they see as being crafted to benefit a particular group that they are not a part of. That's not how copyright was intended, or how it used to be, but as copyright terms grow so respect for the law lessens. It is hard to believe that copyright law exists to give creators an economic incentive to create and the chance to make a living from doing so when the copyright term is seventy years after the creator is dead. While it's true that every person is technically able to benefit from copyright protection, few actually have need to do so.
There are some ways to fix this, but they are legally difficult. The first one isn't a policy issue, it's a cultural issue. Culture carves its own course, subject only to a little direction via forceful nudges by those trying to steer it. There's no hope of effective copyright enforcement on an individual level, but there are other routes. Apple, Amazon and Netflix have gone some way towards this by providing a means of legally getting access to desired content that is every bit as convenient as piracy yet also easily affordable. In the end though, I think it just has to be accepted that casual copyright infringement is and will remain rampant.
You could try education campaigns, but these have a poor history. Such things as Don't Copy That Floppy, Knock-Off Nigel and You-wouldn't-steal-a-car have provided rich fuel for satire, but they haven't actually achieved their objective at all. People are stupid, but they are not complete idiots - they can recognise blatant attempts to manipulate them.
The second part is easier though: Shorten the copyright term. A lot. If you did that then you might see fewer people decrying copyright as corporate welfare. This is unlikely to happen though - it would require international negotiations, while being fought by some of the world's most skilled and well-funded lobbyists. You might also consider looking to the French model, rather than American, which puts more focus on the non-commercial rights of individual creators (Attribution is very important) rather than viewing copyright as purely a source of profit and economic incentive. Very few people are going to make a significant amount of money off of works they have created personally, but anyone who has doodled a crude sketch and uploaded it to DeviantArt will be able to take pride in their creation.