it's even worse with cycling. You could get fit cycling a heavy bike around the neighborhood instead you spend thousands to go 100kms. And accidents always happen at the point most distant from home. And you get more flats the further you go
I guess that, when you're racing, you want to win, not necessarily to expend max effort. For a commute where I use a bicycle instead of motorcycle specifically for the exercise, I want the opposite.
So, even without injury, a broken chain even two miles away from town and a bike shop is no fun.
Edit: I just realized nsteel said pretty much the same thing below.