Because they insist on thinking they need way less power than they actually do.
There’s someone in another thread dribbling on about 50mW levels best SINAD. I had to laugh. A 1970s 2xAA pocket transistor radio would put out 3-4 times that.
I’ve run out of power with 1kW per channel and it’s easy with a genuine 200-300wpc to clip amplifiers on dynamic music.
I really do think it's good to know how something performs at 50 mW since that's what you might be listening to nearfield or what you might be listening to in terms of dialogue in a movie. Focusing only on 2V and 4V SINAD or 5W SINAD loses the fact that you do need high performance at lower volumes just as much as you need them at higher levels.
I have moved toward Meyer Sound PA speakers though. So I get what you mean about making sure you have enough power on hand.