It is not the difficulty itself, as it is probably harder to study engineering in Europe or Asia, but the competitive mindset, "every man for himself".
This has advantages, like taking plagiarism very seriously, but also terrible disadvantages, like not working well in groups.
People like Japanese or Chinese are trained in working in groups with disrespect for the individual. The American culture is the polar opposite, they worship individuals disrespecting the team, e.g you wont ever hear them talking about Edison's team(of which Tesla was one of its members), or Steve Jobs'.
Americans love to believe that there is a person that does everything.
Having said that, in some companies they don't share because of fear.
If you create a community like Microsoft's four years ago in which for every team, the "least qualified"(even if all of them are great) is fired, you create a culture of threat and terror, and people are going to protect their selves.
You have also to take care, not putting too many leechers in the same place as the seeders, or the seeders won't be able to solve problems(that they love to solve) because they are babysitters of the leechers full time(something they hate to do).
Some companies do not understand the last point, then they comply about people not sharing.
If you put together a team that admire each other, they share naturally.