As the Ottoman Empire started to decline and become more conservative, they changed tactics. Why did they still allow foreign goods but didn't allow exports of their own goods?

I'm reading Paul Kennedy's "Rise and Fall of the Great Powers" and he talks about the Ottomans' decline. One of points he makes is that "economic notions remained primitive: imports of western wares were desired, but exports were forbidden."

For an empire that's closing itself off from the world, what prompted a policy like this? Just trying to understand.

Thanks! Any more information/sources would be awesome.