That sounds simpler to do than, say, evolving a cogwheel (which does happen occasionally) or actually developing some of these molecules in the first place. It'd be weird for evolution to struggle so much on trying such a simple concept somewhere. This is a process that naturally figured out solar power, a bunch of mechanical engineering properties, various chemical techniques, all sort of fluid dynamics and statics, radiation resistance, sensing and control systems, etc, etc. If it doesn't build things backwards, more likely than not it is because it doesn't work well. The process knows how to do quite complex engineering tasks.