People will cheat anything. I did a fun ride this weekend, a century around Denver, and caught some dude I passed earlier in the ride getting out of a car toward the finish with his bike. It was an un-timed event.

For Zwift, there are cash prizes for high end racing and even slots on pro teams on the line at times. Zwift also ran the UCI world championship for indoor cycling. So there's more pressure on some to cheat than you might expect.