Individual farms aren’t simply a single open field. So, you need to physically drive between locations, verify that this is the correct location, enter the correct settings, ensure each farms resources are separate etc.
I think you’re underestimating the overhead of talking to people. If your doing something worth X,000$ you want some signatures before and after the fact. Even the possibility of driving to the wrong location is meaningful.
But, it’s also little things like the distance a tractor travels before it needs to turn around. Picture painting a a wall with and without windows using those long rollers. The simpler the shape the faster you can go.