Why do we need a car with 350 horsepower? Why do we need a 5 bedroom 3 bath 2 story house for a family of 3?
Because the "bigger must be better" theory of life!
Most people have no clue that an average living room needs only about 2-3 watts of actual power to drive the speakers at 90db sound pressure level. The trick is when there's a peak in the music that needs 100 watts or 500 watts for a millisecond, you won't hear clipping or distortion for that fleeting amount of time when the amp is called on for the reserve power.
This is the reason that the government outlawed specifying home audio amps using peak power. In the old days, if the output was rated at 1,000 watts peak power (maybe for a nanosecond), the actual RMS power output was about 50 watts. Which rating do you think makes better advertising?
BTW, in their infinite wisdom, they forgot to include automotive power amps, so the car amp manufacturers can claim 1,000,000 watts of power without specifying for how long and into what load.
I have a McIntosh MC2500 (500wpc) feeding a pair of Martin Logan Quest hybrid electrostatics to my home theater 9.2 system for that reason. Plenty of reserve.