Why are all the Claude Code skill files I see online completely pointless?

Every skill file I come across looks like this: “You are an expert full-stack developer with 20 years of experience in React, Node.js, and TypeScript. Always write clean, maintainable code.” Claude already knows all of this. You’re not teaching it anything. The whole point of a skill is to fix something Claude consistently gets wrong. Not to explain what a developer is. And Claude gets a lot wrong. Stuff a real developer would never skip: • Performance is never considered upfront. No thought for render-bloc