Because they are extremely inefficient. Most amps are class A,B, or A/B which iirc only output something like 30% of the power they use to the speakers. Class D and T? are much much more efficient (90 ...
I am looking at building a ~80W class A amp for experiance and to save costs. I am looking at the AE Aegis One's (nice kit for about $500 here) to couple it with for now but eventually will go up to ...