The “lead” is often softer and prone to breaking off, leaving a little cone of lead plugging the end of the sharpener needing to be cleared out by opening it up. A pencil sharpener for coloured pencils sharpens at a steeper angle for this reason
The pigment bit in the colored pencil has a waxy base that will build up and jam/get stuck in the sharpener. Graphite doesn’t. It can be used as a lubricant in some non sexy situations.
This. Graphite is a kind of solid lubricant, and you’ll frequently see it be used for all kinds of friction reduction purposes, both domestic and industrial. This also has the added benefit of any graphite based sliding contact being self-lubricating contact. Add to this the fact that graphite is a very decent electrical conductor with decent thermal and chemical stability, and you’ll see that the material underpinning pencil lead is very useful for electrical systems with a fast-moving sliding contacts. Plus, it’s fairly inexpensive. You’ll see graphite be used in all kinds of extremes, from lubricating door hinges to wire contacts for electric trains.
The same cannot be said for the waxy medium of coloured pencils. When it gets into tiny crevices, it’s more likely to gum up systems instead of making them run more easily.
Call it “the self de-waxing pencil sharpener”, maybe put a battery in it and program a self cleaning/de-waxing cycle when a dedicated sensor detects wax build-up.
