Dunno what made me think of this just now. When I worked for IT in a school district way back in the 90s, a librarian told me she kept a supply of mouse balls in her desk because kids would steal them out of the school computers. What I remember about those balls was they picked up dust and crud off surfaces. Pretty soon optical mice came along and they were history.
My school “solved” this problem by letting students use 386 with DOS, Turbo Pascal and Lotus 123 until the early 2000s, when optical mice were available.
Jesus, I was using Turbo Pascal in the 80s. Had no idea it even still existed in 2000. Flex: I wrote my own BBS in Turbo Pascal and ran if for a couple years in Portland - Tomb of the Unknown Modem.