Is wine ever made in very small batches or even individual bottle amounts?

As I’m getting into winemaking, I’m noticing a lot of recipes are listed by gallon amounts, is there a reason why that’s the particular measurement, and not like half a gallon or third (though I suppose that could be scaled) or even as small as one individual 750 ml bottle’s worth of wine? As someone who enjoys making tester batches of foods and drinks, is that too small to work with? Why?