Indeed. I remember clearly asking my high-school teacher why, if photosynthesis was so simple, didn't we use it to produce sugar artificially? I felt a little irritated that it turned out we spent so much time, and put so much emphasis on such a simplistic model... when apparently it wasn't very useful for any kind of analysis/further work etc.

There is absolutely an art to finding the correct way to simplify models. I'm reminded of Alan Kay's comment at his Ted talk, where he holds up the Gapminder-project for a useful simplification and highlighting/illustration of (rather complex) data, and derides a 3d model of biological processes in cells -- because they show proteins magically dancing stately around and matching up to form reactions -- which is completely different from what is actually happening (large complex molecules spinning really fast, thus making the incredible improbable matching of to such proteins just so possible).

That said, when it comes to mechanics, I think most realize that the model is naive -- students don't feel "deceived" -- and the ratios etc do actually translate to some useful intuitions when doing real-world work (eg: clearing rocks with wire, winch and tackle).