I think the point is that if you are using game data then the only times the offense is currently going for it on fourth down is because they have some reason t

I think the point is that if you are using game data then the only times the offense is currently going for it on fourth down is because they have some reason to believe they can make it with a high percentage. Football is not played with random number generators, the coaches and players understand the matchups and the chances they have of making X yards with the players and plays they have available. The teams that didn't go for it might have a reason to believe that with the players on the field the probability of them getting X yards was small.