A driver with a warning light does not know what is wrong or what it should cost. He is nervous about being taken for a ride. So he searches, sees three shops on the map, and picks on rating and review count, because that is the only evidence he has. Your work is better than the chain two miles down the road. He has no way to know that.
You know you should be asking every customer for a review. You mean to. But you are under a car, or on the phone with a parts supplier, or explaining to someone why the estimate went up, and by the time the day is done the last thing you want is to chase anyone for anything.
So the review count stays where it is while the franchise location, which has a manager whose actual job is marketing, climbs past you. The one-star from the guy who was angry about a diagnostic fee sits at the top of your profile for months, unanswered, being read by everyone who considers calling you.
And the worst part is how quiet it is. Nobody rings to tell you they chose someone else. The bays just have a gap on Wednesday that you cannot explain.