Dunno. If point spreads do a reasonable job of evening the field for both teams, that might not be any different than saying "When you flip a coin, every flip is a winner. ... as long as you pick the right side."
The only way sports gambling can possibly be a profitable enterprise is if there are spreads that don't even the field. And there you would need to give yourself at least a 2 to 3 percent edge to just break even, because of the vig.
That very well may be the case about there being inefficient spreads. ... no market is priced with perfect efficiency up to the moment (for a variety of reasons), but then the problem is how do you as an individual find the spreads that offer value and bet them in a systematic way?
I would bet there are methodologies being used that give an edge of some sort. I am also quite sure that 99 percent of people trying to find inefficient spreads, in a discretionary, non-systematic way, may as well be flipping coins -- actually, worse because of the vig, which makes it worse than a 50/50 proposition. Even if anyone has had any amount of success at it over any period of time, it's almost certainly luck (1 person who has been profitable, versus a multiple of people who have lost money).