Sure, let me expand on my original post.
I see archviz renders on the gallery and assume that the studios producing these images rely on a material library to texture their scenes. I assume this because it would be too inefficient to have to recreate any given material from scratch any time it is needed.
There are services that address this problem by offering subscriptions to material libraries, for example Substance, Quixel, Siger, etc. Quixel doesn't have a lot of archviz textures, Substance is too buggy at the moment, and Siger probably is being used by some studios.
So my question is, how are the professional archviz studios populating their material libraries? Is it from a service, like Siger, or have they simply generated a large number of custom materials from years of experience, and they only use Quixel or Substance to update those materials from time to time when they need to?