I think the difference is that on order to enjoy a non scoring parts of soccer you have to be really into it. You have to try. The NFL had parts that appeal to everyone all throughout the game.
For diehard fans, everything is enjoyable.
For fans with middle interest (which is the bulk of viewers) scoring is a big deal, but the NFL also offers sacks, fumbles, interceptions, or big gains. Soccer offers... No one knows because you have to be super freaking interested to figure out what the hell is happening.
For casual/social fans, scoring is pretty much the only exciting thing. The NFL offers plentiful scoring. Soccer offers maybe 1 score a game if your lucky.
I used to love soccer because I could play it and it was fun. But it lost its charm around age 12. I can't casually watch a game and I don't care enough to invest however many hours it would take to figure out all the crap I need to know to be interested at even a middle interest level.
The only people I've ever met who like soccer are people who played in college. And that fits the theory above. Those people know the rules and plays and action inside and out, they are heavily invested in viewing it as worthwhile since they spent so much of their time doing it, and they feel like they're a part of an experiment club of the enlightened elite (just my experience, not a commentary on you).