Something that is salient is immediately apparent or “jumps out” at you. In this context, I would guess that it’s speaking to the predominance of an activity in someone’s life, i.e., an activity becomes highly salient once it is highly predominant.

I’ll just add to all of the great comments by saying that one of the challenges is money. Take, for example, neurodegenerative disease. There is a huge amount of work being done right now to develop a blood test to screen for Alzheimer’s (Google C2N Precivity). These efforts have tons of money behind them because there are huge benefits to pharmaceutical companies when screening patients for participation in clinical trials. There is not the same kind of incentive for CTE diagnosis, and it is nowhere near as prevalent as Alzheimer’s, so you don’t have the same industry financing and inertia in CTE research.