The full quote is, "A lot of them now will come to cycle shops for pretty much 90% of bike repairs." So not necessarily that 90% of people are coming in for every issue, but that there are people who rely on the shop for almost every issue.

I've learned a lot about bike repairs this year, and I've been volunteering as a mechanic at free bike repair events. It's been interesting going from the clueless customer asking for a "tune-up" to being the one asked for a tune-up. If you ride but don't have maintenance background you know that it's possible there might be some problematic, or even dangerous issue; but you have no idea what that might be. And if you can identify a problem, as far as you know any work you do might brake something in a way you don't understand. So I can understand people going to the shop frequently.