A couple weeks ago I had to travel for work and I picked the longer one because I got paid for more miles and it meant I would get back right at the end of the day so I wouldn't have to do anything else that afternoon. Also on that 2 hour drive I think I saw 5-6 cars for the first 3/4 of it which was pretty great.
I'm guessing they have a job like mine, where a driving trip is a relatively rare occurrence and micromanaging the travel isn't worth it to mitigate the risk of paying out a little more.