If he paid $750 then he’s not a wealthy person paying millions so he theoretically could be part of the problem. But he has had years when he’s lost money. How much income tax should he pay when his income is negative?
If Keri runs the first and fourth legs Dorothy can run the second and third, which saves a handoff. And since over 20 seconds per 100 is record time for them they need every edge they can get.
It’s just good etiquette, like wearing white gloves.