Even if the commuter has to spend the same time on transit, they have time to relax, read, work etc.
This is ignoring the strides we can make with bike infrastructure which provides excercise along with the commute, even in low density suburban areas. Or encouraging remote work, which eliminates the commute entirely and frees up much more time.
Sprawl exists because people want to be connected to cities without paying downtown luxury condo rents, and it's the only viable option (considering public school quality, neighborhood safety, etc.) we're being given.
When the only place where zoning and planning boards allow density is a relatively tiny downtown, surrounded by low density development, it's no surprise prices shoot through the roof.
That's a very America centric view.
Well it turns out driving takes a long time too, but you're really just being a moving couch potato.
Some will not "exercise" unless forced, sure. For others, the best way to promote exercise is to promote free time.