Actually you do.
All of the intense cardiovascular work in all sports, like football, the NFL, etc, is done in pre-season training. It's called 'match fit' not because you get fit during the match but because you arrive at the requisite level of cardiovascular development to be counted match fit when the match arrives.
This is why, in pre-seasons, so much emphasis is placed upon high-intensity short sprint intervals immediately upon returning to training, because it is the best and quickest way to reach a point of being able to play for a full 90 minutes. It's not the playing of the matches that gets you physically ready to play matches; it's the high intensity cardio work with elite level personal trainers in training get you 'match fit'.
This is also heavily emphasised in the Hard Knocks series about NFL training camps. The work you do with the PT's are the main work of arriving at match fitness. Matches are more about tactical cohesion, team fluidity. Elements of mental and intellectual coherence.