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That they find soccer boring because they can't "see" the action.
Same thing with baseball. Something as simple as a 1-0 or 0-1 count on a batter can hold a hardcore fan's interest, whereas to a more casual fan they're just playing catch until the batter puts it in play...
A typical American can't begin to discern whether a midfielder is having a very productive day or a very unproductive one. :- ) Our loss.