I don't really understand why these Certificate Authorities exist and need to charge money to sign a digital certificate. Couldn't some sort of user based distr

I don't really understand why these Certificate Authorities exist and need to charge money to sign a digital certificate. Couldn't some sort of user based distributed network be used for authentication? I mean we trust compilers and code patches (which do see many eyes) that we then load onto our PCs. Why can't we trust some similar mechanism of authority that is user based.