I gave my Galaxy Nexus to my dad, so it saw longer use than usual. After five years it was virtually unusable. It was already slow when I stopped using it.

My Nexus 5, which is sitting in a drawer nowadays, also becomes ever slower. Even my HP Veer, keeping the Nexus 5 company, isn’t getting any faster either—even though it never saw real use.

So yeah, basically all manufacturers “do it”. It’s not even about heavy use or anything.