Playing Devil's advocate, all I can offer is the history of the Sharpie. It performed very well in a variety of uses.

One argument I've heard in support of flat bottoms is that when they heel they present a V shape to the water.

For me, the Sharpie's main appeal is ease of construction. I often think beach cats have become too complex and expensive. In that regard, the market might support a less expensive type if performance remained good.