I do them all the time, and have to get on another report as soon as I finish this post, my 4th so far this month. :-D
It's a big YMMV thing.
I think the amount of work for the gross return is ok for the ones I do. I pay with my Venmo VISA card which pays 3% cash back on your most used category each month, and I keep all other categories under the car wash totals for the month to max the return.
Why I do as many as possible each month is I also drive rideshare, and I like having a clean car for my riders.
I do the green/yellow car washes. Should that program ever go away I would become a monthly membership customer with them. They are all over the place in my area, and I'm kinda hooked on my car always looking nice.
Have synthesizers, will travel...