My guess is the money they keep on these is likely less than what they make on their ordinary products. It makes sense for a company to keep some of the revenue, as even after covering "expenses" there's still likely other resources being used in the production and distribution of the cigars that may not be accounted for in a line item budget anywhere.
Plenty of other manufacturers not donating anything. It's 1 thing if they're marking up prices and using it as a marketing ploy, it's quite another if they're taking in less profit than they otherwise would to donate to a good cause.