I think reading what other people have done is a powerful tool, but it has some drawbacks. First, it's sortof like looking at the answer to a brain teaser -- I now have the answer, but I probably haven't improved my skill at solving brain teasers. Second, it kindof puts my mind in a box so that I'll think about the problem the same way as the people before me, and I may get stuck in the same places they got stuck, whereas if I reinvent the wheel myself, I may arrive at a slightly different wheel that has some advantages over other wheels that I wouldn't have thought of starting from someone else just telling me about wheels.
Anyway, as always, I think there are pros and cons, but I think that people undervalue reinventing the wheel. In fact, I think there is a social stigma against it. I think people perceive it as arrogant -- how can someone think that they'll reinvent a wheel better than the "great" inventors of the past? However, I think this perception is harmful -- how are people supposed to learn to be inventors if they can't practice inventing things that have already been invented?