well you can turn the header off pretty easily and you won't see many sites are breaking (alexa top 100), of course some wierd sites think it's important to use

well you can turn the header off pretty easily and you won't see many sites are breaking (alexa top 100), of course some wierd sites think it's important to use it, but because of the madness of referer there are so many things that will leak your privacy extremly, it came to the point that it's necessary to have extensions to remove the header or at least inject noreferer into a tags.