Not that it really changes your point, but I suspect most dairy farms are small, but most milk comes from large dairy farms. Large farms have orders of magnitudes more cows than small farms.

This is great for the dairy industry, they love to advertise that most farms are small, family-owned operations, which is technically true, while selling you factory farm milk.

(If it's not intuitive, imagine a world with 10 farms with 50 cows each, and one farm with 3000 cows.

I suspect that herd size looks more like a power law distribution than a normal distribution, but a quick google search didn't turn up good data.)