Ever try to find a dimmer rated for the full ampacity of a circuit? Good luck - and, if you find one, it will have a metal cover the size of a dinner plate, just to dissipate the heat.
Even most light switches are not rated for the full current- look closely, and you'll find plenty with straps stamped "10A."
It appears there has never been a requirement for a switch to be capable of anything more than controlling the intended load.
