To shed some light on why it is so hard to think for yourself, it is worth asking a different question: why do other people want you to think like them?
People want you to adopt their perceptive because it makes them feel more comfortable and secure. Their reasons are selfish. For some people, what's at stake is their sense of "good-person-hood". These people have beliefs that make it easy for them to feel like a good person, and by challenging them, you are making them feel personally challenged.
Other people just want to be seen as authorities. When they say something it's to be trusted. It's not necessarily out of power hungriness, though it can be, it may just be that they need to trust what they say, and questioning it to them is equal to 'self-doubt'--an unpleasant feeling of unworthiness or uncertainty to act. Therefore, they take it personally if you 'shake the boat'.
It's difficult to work and live with such people, but such people are not rare. Of course, with enough inner reserve, one can treat these social problem as exactly that, problems--as a thing that can be solved (there are other ways to make such people feel comfortable and secure without risking your integrity. And completely irrational people can be ignored). But how many people have this inner reserve? It is not laziness that is the issue, then, I don't think, not predominantly, rather I think it's a matter of guilt and/or not wanting to burn bridges with people.
The challenge at hand, namely dealing with these social problems, requires a good deal of intellectual confidence, something that is culturally not encouraged. The difficulty with thinking for yourself is that you can't very easily take a half measure. If you think for yourself, but in conflicts you pretend not to and play along with someone else's world-view you'll be miserable. However, if you are going to try and fight your corner and live by your principles, you have to have more integrity than the average person does.
Of course, in having this integrity, it all becomes easier. You commit to finding ways of dealing with people in conflicts so you don't hurt them and feel guilty, if feeling guilty is a problem for you. Or you learn to dislike the idea of having friends who wouldn't bully you for living according to your own values.
