I'm not advocating to go back the old days of closed-group, in-house boys club sports, but let's take a moment to reflect.
Without a visible course or cameras following the race, it has always been challenging to marshal long races (bike, run, swim, horse, car, anything). The reward for winning these races has always been gaining notoriety and therefore sponsorship money. Up until 10ish years ago, the way you got sponsors was largely dictated by WHO you knew. Results were necessary, but a reputation as a fair racer was determined by the tight, largely closed group at the top. Cheating your way into that group would get a stink on you that's hard to remove. So no sponsorships, no money, no motivation to cut courses.
Fast forward to social media days, and the way you generate income now is through your social media. Win a race, everyone follows your account, monetize it with ads, profit. No gatekeepers, no self-policing of the group. Cut the course to win->gain followers->block anyone who calls you out->sell ads on your newly grown userbase.