There are millions of plastic-modellers out there - and they need no torque, just low speed. They now use a pin-vise (no fun when hundreds of 0,5mm holes need to be drilled in a spaceship for fiberoptics) - and other hand driven tools only. Dremel-types just melt the Styrene. I think there would be a market for slow and cheap but slow ones. There are some small battery driven tools of that kind out there - but unfortunatly all of them i know have a not very versatile chuck-type, they are not planned for all this toolbits. So they are not really usable for them.
Well, that´s the reason why i have no use for any of these rotary-tools - but it seems other guys use them with pleasure for their work, on other materials.