Simply put...
It's because they are so small. I know that this sound like a simplistic point of view, but I can tell you this from experience. Yes, I know my pilot sucks too.
Masking and pad-printing hits become expensive at that size because quality control becomes a big problem.
It's not that it can't be done or done consistently. It's just that it's not cost beneficial considering what’s gained. To begin with, half of the market detests the idea of pilots in their models. It has to be one of the most contested issues next to whether chili should have beans in it or not.
This is not the rule but just one reason. We had a much more elaborate pilot designed for our Mustang, but with the factory dragging it's feet and resisting almost everything tedious, we had to make some sacrifices that we really didn’t want to make to get our models on the market. We were eighteen months late releasing our first model. How’s that for a blown deadline.