It is not that support is completely non-existant. Ruby, for instance, can be executed in a PHP-like fashion using ERB.

    $ echo 'hello world' | erb
    hello world
    $ echo 'hello world' | php
    hello world

If a new user could throw index.erb up on a server and have it execute in a Ruby context, would we be any further to supporting better development practices? Will the user take that experience and move into a framework like Rails later? If yes, what has stopped them from using the similar PHP frameworks that will already take them away from the comfort of the single page template?

If you truly only need a single page template without any further abstraction, then why not use PHP? It seems all of the complaints about PHP stem from using it in big projects. It is hard to argue that it does a single page template very well for when that is all you need. Right tool for the job and all that.