Lol, smh.
Because a blocked punt and a fumble (in the scenario you gave) are not the same.
The second a ball is punted, one team (the punting team) is conceding a change of possession to the receiving team, so long as they gain possession of the football. The ball was punted beyond the LOS (that's all that is required); a Cowboys player tried to field that punt; he failed; the punting team recovered.
END.OF. STORY.
First, way to go with the condescending manner.
Second, the ball never travels beyond the line of scrimmage off the block. Take a look at the replay. It is touched after by a Cowboy player only after bouncing beyond the LOS which well short of the distance they were held under when they were trying to regain a fresh set of 4 downs.
Conceding a change of posession or any other football play should always follow the main premise of the game. If you do not gain the requisite number of yards to have a refresh set of downs you should not be rewarded in any circumstance.
Based on the rule we could have had a blocked punt. The ball could have bounded beyond the line of scrimmage, and then took a weird bounce backwards for 5 yards, then touched by a Dallas player who hits the ball back another 5 yards to be secured by a Bronco.
So the overall gain would have been a -10 yards, but a first down for the Broncos. That flies against the common sense and overall tenet of the game of defending your territory.
Even in a conceded change of possession the premise of the yards necessary for a first down should always be tantamount to some odd bouncing circumstance of the ball. Keeping the first down rule rewards the effort the defence placed in preventing the offensive team from gaining the first down that led to the concession of the possession in the first place.
LIke everyone else we realize the rule, but it makes absolutely no sense against the 99.99% of the other plays in this league that maintains the primacy of what a first down is.
Why do you think all the Cowboys players were celebrating when they blocked the punt, and the Broncos never gained the first down marker? They were conditioned to protect from gaining the first down.
Stupid rule in my opinion.