Since the introduction of PBR there has been a problem in the user interface where setting two faces into planar mode and trying to click "align planar faces" while a PBR material is applied then nothing will happen, however with legacy textures the process goes as you would think.

There are a lot of creators and marketplace sellers that use planar align to get things looking near perfect without using baked textures and photoshop.

I think having this finally fixed will see an increase in content on the Marketplace and make PBR a lot more fun to use.