I'm pretty sure that, in most places, a greater quantity of paying rock/pop gigs are available than folk spots. Some of those rock gigs pay better than others. Generally, the more "creative" or personally satisfying the music, the lower the pay. Cover bands can make good money.

You have a point about the setup and breakdown time; people can easily fail to include that when figuring pay-per-hour. I've observed my kid brother ~ an excellent drummer who managed to avoid day-job involvement for many years ~ laboring hard and long before and after every performance. Very stark contrast to the lot of a solo acoustic-guitar-and-vocals act, who can quickly and easily breeze in and out of the venue.