It's the same reason most restaurants offer vegetarian dishes. You're not just losing the business of the few percent that are vegetarians - you're losing the business of groups that include vegetarians.

(The analogy is incomplete since you'll also get people who don't want to get locked out of Linux even though they don't currently use it)

Also Linux users are very overrepresented in the propellerheads group that you are targeting in the takeoff phase of a DB/Drive like product.