If I remember correctly I think there is an extra box you have to tick/say yes too, to allow simple edit interface in the admin screen for them.
edit - also when you apply them, you click the dropdown template box below the content type dropdown. Make sure that asset is included in the selected root node.
I have done that, but I still don’t see an option to set the content template. Is there a place in Matrix where you set the root node for the content templates that you have created?
