why have watts that are unusable, why are they unusable watts?
Because, if the first watt isn’t any good, why would you want 200 more of them?
The reality is even when listening quite loud the vast majority of the time you’re using only a very few watts- and only fractions of a watt when its not really loud. Because if you think about it, a 90dB speaker plays pretty loud with 1 just watt (90dB), real loud with 10 (100 dB), and crazy loud with 100 (110dB). Only 100 watts, and so loud its hearing damage.
And yeah, yeah I know: distance. Whatever. Its still loud.
The above by the way is in impotent solid state watts. In manly tube watt terms 30 watts is plenty. In multichannel home theater terms no amount of watts is enough to sound as good as 30 quality tube watts. Its kind of like, you can have a whole army of Ben Stillers, its never gonna amount to one Arnold. Or to misquote another famous actor: All your watt are unusable to us.