How could they? They can't just disable autoplay but make an exception for YouTube, that would be wrong in so many ways. You can't make that into a web standard, so it would promote browser fragmentation, for example.
So how about a whitelist/blacklist? Well, since users can't even agree among themselves on which websites belong on which side of the fence, such a list would quickly become a nightmare to maintain, still be based on someone's personal bias, and would still leave small websites at a disadvantage.
Pretty much the only thing that would work is a permissions question to the user, like there is currently for e.g. location access. "Do you want to allow videosite.example.com to automatically play video content? \Allow, \Allow and remember, \*Deny"
So how about a whitelist/blacklist? Well, since users can't even agree among themselves on which websites belong on which side of the fence, such a list would quickly become a nightmare to maintain, still be based on someone's personal bias, and would still leave small websites at a disadvantage.
Pretty much the only thing that would work is a permissions question to the user, like there is currently for e.g. location access. "Do you want to allow videosite.example.com to automatically play video content? \Allow, \Allow and remember, \*Deny"