Mixture of motor technology, cost, and application. Take a dremel for instance, adding all these features cost money and most dremel users won’t care for it. Al

Mixture of motor technology, cost, and application. Take a dremel for instance, adding all these features cost money and most dremel users won’t care for it. Also certain motor technology makes it impossible to control in a meaningful fashion. If you stuck an encoder on a dremel, you’ll still have a lot difficulty maintaining the set RPM.