expense, weight, and lack of flexibility. A fabric sail can easily be reduced in size by lowering it partially when the conditions call for it. Weight aloft m

expense, weight, and lack of flexibility. A fabric sail can easily be reduced in size by lowering it partially when the conditions call for it. Weight aloft must be counterbalanced in the keel in a monohull. A solid sail requires heavier supports than a fabric sail. Expense. A fabric sail can actually make a pretty good airfoil, rigidity adds an insane amount of expense to get you a level of performance that doesn't really matter to most.