The goals don't have anything specific to do with the user. They don't "care" that I was overweight last January, but not overweight now. They don't care whether I am happy at 160# or want to get down to 150#.
But they do "care" how many calories I burned the last few months or how many miles I ran.
I wouldn't mind seeing customizable goals for weight, miles, calories, VO2max, etc. It would be a nice feature. As it is, the Watch may challenge me to run 300 miles in April at a time when I'm cutting back for my goal marathon.
As for running high mileage, no one starts out running 70 miles per week, not even Tony Stark. It usually takes a few years to get to that point. And even then, it's not 10 miles every day. During a marathon training cycle, I might run 6-8 miles four days in a week, 10-15 miles two days, and 17-20 miles one day. That adds up to 61-82 miles. And usually only one of those runs will be hard/fast (and maybe the long run). The others will be slow/easy. At almost 50, I can't handle the two workouts and a long run that a high school or college runner might do.