I think I was just being too low-level, lol. I was basically saying what you’re saying: it computes colors for the gbuffer. I was trying to emphasize that materials are meant only for colors, not lighting, and to keep lighting calculations (e.g. like trying to fake lighting) out of the material. This would explain why materials are very stripped down from blueprints (no exec pins, no loops, no and/or nodes, etc.), whereas shaders support all of that.
Kinda off topic, but applicable to optimization, I guess.