Our belief, seemingly validated by experience, is that the overwhelming majority of people in Western-like cultures are basically honest. While, in this realm, we have no meaningful experience with people in other cultures, it is well documented that some cultures have integrated product piracy to a significant extent. Even so, it's still our belief that the majority of people are basically honest, regardless of the cultural influences.
However, when software piracy is made too easy, people are more likely to conclude that it's OK. This has long been the situation with photocopying printed material and quickly extended to copying software.
Today it's even worse because software is commonly distributed electronically. There's strong evidence that, when it takes a trivial amount of effort to find a simple license code for a software product, more people are willing to do so and thus pirate the software. As soon as you make it more difficult, the vast majority of those individuals become compliant. This is not unlike many other areas in life (e.g., deterrents "help" us obey traffic laws).