Initially, it had to do with a lack of knowledge. Farmers were already satisfied with their drainage systems. It's important to note that we hadn't experienced any drought-plagued summers like the ones we've seen in the past decade. Over the past five years, we've had three very dry summers. From what I've been told, the practice helps retain moisture in the soil for at least two weeks longer than an area that's been drained.
On February 5th, 2018. See this statement in context.