It's not just football. All of my boys played soccer. One played football until a bad concussion his sophomore year. I saw the impact. One of them lives with some long term effect, though two of them are engineers and one an attorney. As a dad I feel responsible to a degree. The football concussion was from direct football contact. After the hit, he had 2 interceptions, one in the end zone and a pick six. That said, I could tell something was wrong and like all good sports parents I sat there.
The soccer concussions were rather random and of the 5, all were contact with the ball, but not intended heading. One was actually over a girl the 2 players from opposing high schools were competing over. A stellar basketball player, he didn't start his senior year from the hit at the end of September and at Christmas still struggled to catch passes. After the Holidays he got back his starting position (and got to play against a number of Big starters).
No one will convince me that there won't be long term issues. The middle son struggles with social anxiety (the other 2 not at all) and he knows somethings wrong. He does appear to be getting better.
What is interesting is that 2 of them easily get concussion symptoms from not hard contact playing pick up sports.
It is so common. Ask a parent of a player in a crowd, they'll say their kid never has had a concussion. Privately, they'll say things like....well, he did get dinged pretty hard a number of times.
I had a bike wreck several weeks ago, breaking my helmet in two places. My headaches come from the opposite side of where I hit. Been a bit groggy and sleepy. Also been on coasters where afterwards I had concussion symptoms.
I do think football helmets are part of the problem, but also a strong shoulder hit to the mid section causes a quick deceleration and then acceleration the other way. That repeatedly has to add to the problem. Getting hit or tripped and hitting the head will happen without helmets.