All individual sports using same coaching model. Same for that matter as any musical instrument or other individual pursuit.
I think that's an interesting comparison. When I was a beginning musician (which was not in the US, so band class was not a thing), my instruction was provided in a small group setting with others at a similar level. As I improved, I moved on to private lessons and then to a teacher who could teach me more specific technical nuance. I still played in groups, but my "real work" was done individually.
My tri club functions in a similar way. We have swim groups, run groups, and bike groups. They're fun, coached by real coaches, at a level slightly above the lowest common denominator. Beyond that, perhaps you join the small-group coaching specifically provided outside the club by the swim coach, or you take lessons with her one-on-one. Maybe you join a group of roadies to get a more aggressive road experience, or you have a cycling coach who works on aspects of your riding and how to best use that fancy power meter. Or, you get a tri coach who covers maybe strategy and how to magically make ten more hours appear in your week moreso than sport-specific technique.
It's not unique to tri. I have a friend going through this with cyclocross right now; she's been a part of the general coaching group for several years now and has decided that she wants to make a real, concerted effort to cat up. She's hired a coach to supplement what the group gives her.
Eventually, I think with most of these things you end up at a point where what you need is so individualised that the most efficient way to provide it is individually.