Nicko. said:
We see the core of sport.
No one is paying to watch, no one is getting payed to participate or for winning (?).
Participants are in it for personal joy/excitement/experience/challenge.
I like what I see. Doping can still be a factor.
That is part of it. I would also argue that an athlete who enters a local fell race, in his club vest, for fun and nothing else, does not fit very well the profile of someone determined enough to win the big pro prizes that they would dope. There is a substantial risk of injury in a fell race. That event that Brownlee junior is competing in (Chevin Chase) has plenty of ankle snapping potential. He's clearly not hanging about either because the athlete behind him is an international class mountain runner.
The instance I previously referenced was J Brownlee running the Yorkshire X Country championships for his club, whilst carrying an injury, in Olympic year. He actually aggravated the injury during the event.
Both brothers regularly turn out for fun at these "doing it for the love of the sport" fell/x country races. It doesn't seem to me to be consistent with a "win at all costs", "professional" attitude to sport. Why take the trouble to have a doping programme if you're going to risk a broken ankle running "meaningless" fell races.
I can tell you why they do it. It's because they grew up running these fell races as juniors. They love them ... as do all the other participants. It's a big part of sporting culture in their part of the world. And it's fun.
Edit: In answer to Nicko, the prizes for most of the fell events they run in are things like chocolate, wine or maltloaf (honestly).