I import an .obj mesh with .mtl and the corresponding texture image to Blender under cycles engine. The structure of the imported mesh looks like this, under the "jacket" material there are already an texture image named 05.jpg:
However cycles engine can't render it correctly, there's no such texture shown in the result:
Some posts say that the cycles engine isn't able to import texture automatically. So I assign an image texture to the two materials by nodes:
Now the engine can render it in a correct way:
So my question is, since under the material tree there are already texture images linked, why I still need to create a node to assign that texture image to the material? Also, There are many materials and some of them doesn't require image texture while others do, how can I repeat this procedure by script?