What’s wrong with using robots.txt directly or possibly something like fora.txt, following basically the same syntax as robots.txt? – allowing you to forbid all

What’s wrong with using robots.txt directly or possibly something like fora.txt, following basically the same syntax as robots.txt? – allowing you to forbid all aggregators/social somethings/fora/a specific whatever to link to you. Not that I would be particularly fond of a web where you have/are expected to check with a given site in order to be allowed to link to that site…