While I agree with you that the lack of concurrency is problematic in the long run I think that JavaScript on the server will be at least as useful for many web

While I agree with you that the lack of concurrency is problematic in the long run I think that JavaScript on the server will be at least as useful for many web applications as PHP, Python, Ruby, Perl - all of which have modest or non-existant concurrency stories. I'm curious as to why you think JavaScript can't hold it's own weight against said-languages for the server-side?