In theory you're right, but probably not so in practice. Football players would see the consequences of the change much more quickly - they'd go from being able

In theory you're right, but probably not so in practice. Football players would see the consequences of the change much more quickly - they'd go from being able to dive at a player head first and have a cushioned impact to having their skull connect with something hard and feeling a lot of pain. I'd expect their behaviour would adapt in response to that. Similarly car drivers probably wouldn't drive any more safely until they experienced the consequences of crashing while not wearing a seat belt.