It is my understanding that the cast members operating the monorails are not allowed to operate in reverse, for safety reasons.
Because of this, when they switch directions, even just to go back to the barn, they have to switch to the operating cab that will be in front for the new direction.
Now that may seem like a simple thing to do, it is not.
They can't just walk into the cab, push a button, and go.
When they get into the other cab they have to go through all the safety checks just like they do at the start of the day.
All the instruments, controls, and communications in that cab have to be checked.
And the paperwork filled out.
This takes time, guessing about 15-20 minutes if everything checks out ok.
Doing this at the end of the operational day adds all of those 15+ minutes before they can proceed back to the barn.
Doing it in the middle of the day, they can do most of those checks while guests are unloading and loading.
Very little delay for those guests, who probably will not notice at all.
Since they will not have to change directions at the end of the day now, once they drop off the last guests, they can proceed to the barn with no delay at all.
Maintenance and cleaning can start 15+ minutes sooner.
That may not be a lot of time, but how many times have we wished we had 15-20 minutes extra to finish a task at work?