On to the topic at hand:
I don't think anyone outside of amplified musicians going for a particular sound really likes massive distortion. A small amp rated at 10% distortion is probably doing so because they want to sound like they have more power than they have. If the amp has 10% distortion at 10 watts, it may have a good clean 2-3 watts. With moderately sensitive speakers that are 90dB/watt/meter 2-3 watts may be enough for many listeners, and a high efficiency speaker rarely needs more than that. If you want High SPLs, short of a <100dB/watt/meter speaker you will certainly need far more undistorted power.
Why do people like these amps? There are probably as many reasons as listeners, but some probably appreciate the sound produced by a very simple circuit. I am sure others simply like the idea. I have used some of these amps on tweeters and found them quite pleasing. I have never tried one on a full range system.