This isn't exclusive to the Pigeon-hole Principle, either. Many named conjectures are pointlessly used, just because they're named, even when it makes the proof longer.
This isn't just exclusive to mathematics. It's similar to the reason people bring in single-line Node.JS packages; a fear of re-inventing the wheel when they don't actually need a wheel in the first place, or when the wheel is trivial to re-state in a more natural form for the proof / program.
This isn't just exclusive to mathematics. It's similar to the reason people bring in single-line Node.JS packages; a fear of re-inventing the wheel when they don't actually need a wheel in the first place, or when the wheel is trivial to re-state in a more natural form for the proof / program.