Yeah, it's a series of tradeoffs though. The thing is that with flats, if you are overusing something in your leg your foot will move around a millimeter or whatever so that it doesn't cause you a problem. With clipless your foot can't move, so if you're rubbing something wrong inside your leg you're stuck.

It's easier to set someone up from a fit with clipless, but more difficult to get them properly fitted to begin with. Clipless can cause people issues that don't have issues with flats. Like personally, 2 fitters and 3 pairs of shoes did not cure my knee pain with clipless (that I did not get with flats). I happened to start doing barbell squats and when I got the form right, that actually fixed it, but but the problem was more than just a fitting issue.