1) Does every website have a robots.txt file?
2) Is every websites robots.txt file publicly accessible/downloadable - if so from where?
3) What is the point in them, for example if you have an entry in robots.txt for /admin - then if the file is publicly accessible then what has it actually solved? I.e. how are you any better off in hiding /admin from google if someone can download your robots.txt and then see you actually have /admin directory on the server?
I cant see the logic or what the point in adding entries in it are?