Electronic dance music is the biggest genre in the data. So then easy to play shouldn't matter. It's still an interesting question. I think playing Db is pretty nice on the piano even if it's not the easiest.

There is a sweet spot for the bass. Lower is better for deep bass, but too low and it stops being a recognizable note, and consumer speakers can't reproduce it. This effect exists though I'm not sure if it is the cause of the pattern here.