When I think of matrix multiplication in graphics I primarily think of transforms between spaces: moving vertices from object space to camera space, transforming from camera space to screen space, ... This is a big part of the math done in regular rendering and needs to be done for every visible vertex in the scene - typically in the millions in modern games.

I suppose the difference here is that DLSS is a case where you primarily do large numbers of consecutive matrix multiplications with little other logic, since it's more ANN code than graphics code.