For me I do workouts to train for back country hiking. So many of the workouts are timed with many rounds where you are tracking a goal. I have a Garmin that I have programmed several of the workout types into so I can see my overall time, current round time, current round count, and total count. I also use it for timed weighted hikes were I can track my elevation change and heart rates.

I never had any obesity problem even without exercising: what problem is exercise really solving?

The fact that I don't need something to achieve a particular goal does not mean that others don't.

In all fairness, you do recognize that there might be goals other than encouraging exercise, as you wonder what they are.