Perhaps because most defenses are also incapable of winning a low scoring game?
That's what makes defenses who CAN so special, like the 85 Bears, 2000 Ravens, last year's 49ers (especially considering the "era"), etc.
However, scoring isn't up all that much.
In 2000, teams scored 20.7 points per game.
This year, teams scored 22.8 PPG
The range in 2000 was 10.1 PPG and 33.8 PPG
This year, the range was 13.2 PPG and 34.8 PPG
In 1980, teams scored 20.5 PPG. The range was 14.4 PPG to 28.4 PPG
What may have happened is that the top offensive players can take advantage of the rule changes, and like you said, you need a QB. All the illegal contact rules in the world won't help if your QB can't hit the open man.
The top offenses have gotten better. There's 5 to 6 points per game difference there in the last 32 years. But the bottom offenses? They still suck.
If you suck, you still suck. If you're good, you're getting some aid from the rule changes.
The question is going forward, imo, "Will there be enough top-level offensive players for all teams to benefit?"
If colleges are putting out a higher number of better
NFL-level talent, then scoring could suddenly skyrocket if enough teams get enough of these talents. High college stats doesn't mean better NFL player. Of course, the answer at some positions and for some kids won't be known for some years yet. Not all good QBs in the future will necessarily take the Luck, RG3, Russel Wilson path. Some might need some time to mature and develop. Some might need more weapons, etc.
Of course, colleges are going to keep producing defensive talents, too. The next Ray Lewis or Patrick Willis or London Fletcher is out there somewhere. Next Deion Sanders, Darrelle Revis, etc.
And, as was mentioned, I agree that defensive coordinators are going to figure SOMETHING out. Wildcat looked unstoppable...until it was stopped. This read-option stuff will be doable only by a select few special players with unique skill sets. And there's always new coverage schemes, blitz packages, etc, to try to stop QBs.
I mean, look at P. Manning? His offense produced just 21 points - right at league average. It was that tiny speedster Holliday that did the quick damage. It was the break downs in the secondary that got the Ravens at least 2 of their TDs. Take those out and it's 24-21. Ho hum.
Special teams is a big deal now, too. Teams try to have a return specialist. Teams realize that driving 80 yards on any decent defense is tough. Even bad defenses are still NFL defenses, which means someone can make a play at any time. "Bad" is just relative to the elite population that is the NFL.
Then throw in events like favorable turnovers (getting a pick on your 9 instead of my 9. On my 9, I need 60 yards to have a decent chance at 3 pts - on your 9, I'm almost guaranteed 3 with high chance of 7)
And small sample size indeed.
In 1980, these four scores happened:
41-35 - New York Giants defeat the St. Louis Cardinals.
41-20 - Detroit Lions defeat the L.A. Rams.
51-21 - L.A. Rams def. Green Bay Packers
37-27 - S.F. 49ers def. New York Jets.
Back in the 'low scoring days'. All in the first three weeks - and that ignored a 42-7 blowout, 35-3 rout, and other 14-21 pt spreads (the idea that football games are almost always close would be interesting to examine - I think it's 50/50 whether or not a game is decided by 2 scores or more)
And yet, in baseball, it was the "revival of the pitcher".
They could move the fences in - pitching would suffer, until it is figured out how to stop the balls from flying out. Maybe the groundball pitchers would start to dominate the player population. Only flyball guys with insane K/BF and BABIP totals would survive, etc.
Sports is a self-selecting arena, no matter how it changes. I think that will keep things within a certain range until the change is so large, it impact player populations as a whole (everyone is as good as Randy Moss, etc).