That, and the fact that we don't really revisit the modeling approaches when the constraints that led to them no longer apply. For instance, incremental evolution based on a branch where work was done "by hand" into animals, simpler machines and then very complex machines might lead to a very different result than evolution from a branch where the ability to design some types of complex machines is there "from the start".

Note that this is different than saying "let's completely ignore the past".