If your sand is native and natural (varied particle size & shape), and sitting on yet more sand, then it's the very best drainage you can get.
That's what we have here, in central Florida, where we get frequent torrential rains and in summer daily afternoon showers. The sand can clear flooding in an hour or two, and we don't have to do any maintenance in the runs.
If we added organic matter, it would just stay soggy. We have that problem with leaves and stalks from the Alfalfa hay we give sometimes, and then it molds because the rain and humidity won't let it dry out, so I do have to rake that stuff away before it goes bad.
Sand becomes a problem for people when the drainage underneath is insufficient, like sitting on top of clay, or flat flooring... and when they choose sand without natural variance, like play sand. Even construction sand, which is a step up, is not as good as sand worn by the elements.
There's a reason beach sand is so sought after that it's ruining our beaches under the guise of "improvement"
