It's impossible from a manufacturing and marketing standpoint to produce an amplifier such as you suggest. It would limit the setup options far too much to make it economically viable. So, what is the status quo is likely to remain.

I do hear what you are saying about excess power though - my mains are powered in an active bi-amp setup with just 60 watts for the woofers and 5(!) watts for the tweeters. But I'm in a minority of perhaps a handful of people on the planet who go this route.