I don't think we're seeing a rise in the actual incidences of concussions and sports-related neurodegenerative diseases, so much as an increase in the public discussion (and a generally increasing sense amongst the sports fans and sports media that the problem is serious and needs to be addressed) of said conditions. What's changed, to answer your question, is that people are more aware of the severity of a concussion and the ethic amongst coaches and players is slowly drifting away from "play through it".