Just wrote a little Medium article about your post, as your comments about car culture made me wonder:

Will Autonomous Cars & Mobile Gyms Help With America's Obesity Epidemic: https://medium.com/@nicolaerusan/will-autonomous-cars-mobile...

Def, the nutritional issues are still there & so are the issues around communal activity - but I think for a lot of people I know who have long commutes to work, the opportunity to exercise in transit would be compelling.