The reason? Despite the new tablet’s processing power and capabilities, it’s still running on mobile software — and developers aren’t totally convinced the economic incentives exist in the App Store for iOS. In short, they feel they wouldn’t be able to charge users the amounts they normally would for a version of their software that runs on a desktop.
I called it shortly after the iPad Pro was announced. Pro apps require pro pricing, and the App Store as it is does not support any business model that includes that.