Friction drive is VERY dependable, probably the MOST dependable drive there is. No chain wear, adjustments, tensioner problems, belt wear-breakage, etc. Simple, cheap, basic, and reliable are what friction drive is all about. Yes, running through water is a problem, the answer is to pedal assist the engine and to learn to "feather" the throttle lightly. Yes, friction drive wears rear tires faster than other drive systems, but the cost of bike tires is faily low and wearing out a tire a year instead of every 3 years isn't exactly catastrophic. Wear isn't a serious problem if the drive roller is precisely perpendicular to the tire. I just bought a new tire for my friction bike for next year, $14.00. Meh.
YEP, I agree 100%. With a good motor, they are the most dependable drive system && the simplest.