[dman]

As far as open source is concerned, it might be helpful to split the projects into two categories before examining their motives 1) Corporate driven projects. Here the need to reinvent might be due to profit based motives, or it could be because someone is trying to create work for themselves. 2) Volunteer driven projects. In this case I think it's the geeky need to understand things from first principle that drives the reinvention. The fact that for poorly documented projects the cost of reimplementation early on is comparable to rewriting from scratch doesn't help. Also large projects seem disorganized and bloated when compared against a new naive implementation with few features.