I don't understand the response from Chandon. I haven't been a member long, so I'm probably missing something.
I thought Bolter's reply to What ever happened to just going outside for a ride? was reasonable. Some people can't just go outside for a ride.
And as already mentioned, it's also another way for children to mimic the parents. If the parents have an exercise bike/treadmill the DC can go on theirs at the same time.