Maybe that's because boxing doesn't stop a lot and is meant to be played in a short period of time while American football is more a military game of attrition with tons of breaks between skirmishes.
Or are you just being willfully ignorant about this?
Is that question really necessary? While the question is not directed at me, I AM ignorant to American football. Not everyone is familiar with the way American football is played, especially those from other countries. Your description does shed a new light on it - but I still don't care for it.
Apologies, the normal trope on the internet is to be stupidly ignorant about American football as an excuse to insult it. "Lol handegg rules are so strange! Who would have thought Americans would like watching people stand about for hours!"
Or are you just being willfully ignorant about this?