Why do Class C's always leak in the front upper bunk area?

Someone told me a few years ago: "Imagine if your stick house was subject to an earthquake for 4 or 5 hours a day, it would start to leak and fall apart like a RV does".

I think a lot of time it is build quality but a lot is also we just don't take into account how much stress we are putting on these units and how much we need to do to keep them in good shape.