Do you have any possible explanations on why the Silph Scope hasnt been used, upgraded, or needed since Red travelled to the Pokemon Tower in Lavender Town?
I have a couple theories why:
It was discovered that every one in the world(of all regions) already possessed the ability to see Ghosts, and the Silph Scope was no longer produced.
Ghost-types have become closer to humans, and akways make themselves more visible, getting rid of thier annonymity.
Try not to mention Gamefreak or anything about the physical development of Pokemon.
Btw, I dont just mean in the video games, but in anything related to Pokemon :)