"So why the hell do people buy inefficient speakers?"
Speaking only for myself, I buy speakers that:
A - fit the space I have for them; and
B - sound good to me
In my case (home office/desktop audio), the speakers that fit the space and sound best always turn out to be sealed/acoustic suspension 2-ways. As it happens, that type of speaker design really does tend to sound better with more powerful amps, mainly because so much power is required to move the woofers harder and harder w/increasing volume as the frequencies drop to neas the speaker’s resonant frequency (bass reflex designs operate more permissively near their limits).
But having said that, it’s probably not true that an amp twice as powerful as the one that can happily drive a given pair of sealed speakers, would necessarily sound better. More like the amp that can happily drive sealed speakers to fairly loud volumes has to be more powerful than one that would happily drive bass reflex speaker to fairly loud volumes.