The way it worked for me:

Go out of my way to make things better -> get promotion and pay raise -> go out of my way to make things better again -> no promotion or pay raise -> do the absolute bare minimum -> big pay raise

Maybe they thought I enjoyed improving processes just to do it and saw it takes money to keep me doing it once I stopped.

Or maybe the forces that determine whether I get more money are beyond my understanding.

No graphite on the roof.