Why has amplifier power become a big issue

Modern Class D amps are very efficient and solve the problem nicely.    Without them I'd be more prone to go tube amp (not efficient generally) and high efficiency speakers to pick up the slack there. 

Power specification is very vague.  Average music power is only a few percent of the peak power.  Headroom of the amplifier is very important but most of the time not even specified.  

I also enjoy  my class D amp, especially at lower volume.  It does not loose composure, provides perfect imaging and strong bass.  It is closer to tube amp, in sound, than any SS amp I had.  In addition many amps, including my class D amp, have soft clipping, protecting tweeter from excessive amount of HF harmonics.

I think class D amps are modern marvel, but they don't truly solve the problem.  Feeding mega-watts into a moving coil loudspeaker will result in thermal compression unless you over build the loudspeaker which makes it too massive to properly respond to transients.

A 93dB sensitive loudspeaker with a 50 wpc amplifier will have an equivalent max volume as a 85dB sensitive loudspeaker and a 300 watt amplifier.  I just think the former is a more elegant solution.