Examples usually cited are well-worn bicycles, the steering wheel on a vintage car, a leather wallet, etc. Seems related to patina but not exactly the same. What drew you here is a neologism.

E.g., to be able to e-mail him to reply to questions or queries he asks about the e-mail. “The _____ of the steering wheel speaks to the years of use and loving care John put into his Roadster. Interesting,

here they call it “aesthetics of use” but I’m certain there is a single term.