Obviously these guys have a service to sell and they want to show the value they add over cheaper alternatives, so they'll be pointing out potential pitfalls of competitors.
I don't really get going to see Mr Hand Job though. For 6 quid, and slightly less time, you could pressure washer on a petrol station forecourt and not drag someone else's dirt over your paint. Even if they rinse out cloths, sponges, mitts, towels in between washes, with those volumes they're not going to be replaced that often and will be full of grit/dirt. I chuck away MF towels after a few uses as they start to pick up all kinds of stuff. Say that constitutes 5 or 6 washes for me, for a volume trader that's maybe an hour or two of business. At those low margins, I'm not sure you could afford to chuck away towels at that frequency
Anyway, I'm not saying people who use them are bad or lazy or anything untoward, you can do as you will with your own car, my neighbours no doubt think I'm mental when I rub her all over with a giant towel
I just don't get why you'd go to them over a quick pressure wash.