It's not like athletes in these sports are risking their health and well-being for any great cause, it's to entertain a large group of morons.
The issue of whether the job serves any essential purpose to society is irrelevant to the issue of whether it is rational for a given individual to take the job (in this case, Sherman).
Ah, because one needs one health and body to get through all of one's life and not just your twenties and thirties. Money doesn't help when you walk like a 60 year old man when you are in your 40's, or you have Dementia pugilistica from multiple concussions.
There's no doubt that the job entails an increased risk of cognitive problems later in life. But just because such risks exist doesn't mean Sherman is stupid to take the job; that depends on the level of risk involved plus his own interests. For example, the best data I could find just now indicates that "players ages 30 through 49 showed a rate of 1.9 percent, or 19 times that of the national average, 0.1 percent [risk of dementia-related diagnoses]." (
http://www.nytimes.com/2009/09/30/sports/football/30dementia.html?pagewanted=1)
This means that for an under 2% chance of dementia-related problems, Sherman gets to earn at least 9-10x the median income or so doing the thing he loves, the thing he was in some importance sense born to do. Alternatively stated, assuming that if such a diagnosis were handed down Sherman would be rendered a vegetable and unable to utilize his fortune (an extremely simplifying assumption that is absolutely false), the value of his earnings will be something like $4.9 million instead of $5 million (he will clear this amount unless he is knocked out early, as his rookie contract already has him slated to earn $2.2 million and he will fetch far more money his next contract, given his excellent performance).
Clearly, he is acting as almost any intelligent person would, and you are the fool.
These sports are like Christmas, for the children. It isn't any wonder that the word FAN is short for FANATICAL!
Have you ever considered the possibility that you are the most fanatical person on this board, differing from other fanatics like ahmed only in the specific beliefs held? You might want to consider doing so.