Some people do have fit problems and its because of prior injuries maybe from other sports or accidents, or over use. This translates to bike riding which is mostly a repetitive action. I don't think the human body was designed to ride a bike or to be a couch potato either.

Run and walk (hike)? Yes, more than bike. All the adjustments (fit) are about compensating for this bike thing. You get dialed in so that it feels comfortable, tolerable to your body.

Spawning of a niche: test riding for a week is something I would like to do. Maybe even two weeks, depending on circumstances. For a price of $500, you can have the frameset and groupset and a fitting. An additional fitting would be $100.