[opinion-is-bad]

Just a few: Tractor amortization over additional acres. Administrative overhead rarely scales linearly. Better prices on inputs from ordering in larger quantities. Access to new tech that is too expensive for smaller operations to justify.

A farm is very similar to a factory in many ways. You buy inputs (especially Nitrogen) and convert those into a usable output using biological machinery. This becomes especially true for people planting permanent crops (I.e almonds) where you also need to consider the maintenance on the plant (pruning, etc) as it ages. Uniformity of process is actually another place that large farms benefit. They can afford the quality managers capable of designing such systems. An owner-operator with one guy working part-time for him is less likely to bother.