So there's generally an optimum time of year for each step, and being a couple weeks early or late can definitely lower yield a bit. Big agriculture can stagger planting so that a smaller number of machines can be used per acre, if that's more profitable overall, even accounting for the slight reduced productivity. A group of families can't do the same thing nearly as easily if it means that one family makes a large profit (they hit the optimal time), another family makes a small profit (a week or two late), and the unlucky family possibly makes no profit at all (even later/earlier). In order for this to work, they'd also have to share profits, and at that point they've basically just merged.