Responsible (directly or indirectly) for quite a few of them, mostly oldish and wheezy; I’m not myself mechanical; and we use the shop mostly for routine maintenance—rotate the tires every few thousand miles, swap the brake pads, deal with the oil changes/fluids/filters, etc.

Partly as a preventative measure: we trust them. In the rare cases when they find something, it’s real. As a consequence we get ahead of brewing problems.

Plus loyalty, to some extent; we try to throw work their way when we can, even if we probably could handle it ourselves. The relationship between our families goes back a good 60 years by now.

Fully grant that my situation is unlikely to be representative. And no shade toward OP—it sounds like a cool project thoughtfully done, and a real improvement over the status quo for her relative!

Plus, maybe the customer would prefer to support a business that invests in and employs from the local community, even if it costs a little more. Or they see it as a quality signal. If I call a plumber who outsourced their reception to a call center to save a few bucks, I'm starting to think, "What else is he willing to do to save a few bucks?"