PHP has grown like wildfire and any hosting provider worth their salt supports the usual languages for CGI scripting, including many important modules. But why do so many major providers still lack support for webapp frameworks?
PHP is not a framework? Not sure what you are asking (or rather why you cite PHP when talking about webapp frameworks).
In any case, if by "major" you mean HUGE like godaddy or dreamhost? or some other unknown "big" player I have no knowledge of, it's because the majority of people do in fact use php for their applications. Ruby is popular only in the superCool underground world of github and company.
Point is the answer is in your question. Less people use node.js and rails, and django, so less providers are going to support it. Wide support = wide usage (im assuming)
Because those using a framework do not dev directly on the server. I dev locally and then push full projects to my servers when complete.
Now if your question is why isn't there a one click install for local dev... i'm sure it exist in one form or another. For example Python has easy_install and pip. (pip install django)
In any case, if by "major" you mean HUGE like godaddy or dreamhost? or some other unknown "big" player I have no knowledge of, it's because the majority of people do in fact use php for their applications. Ruby is popular only in the superCool underground world of github and company.
Point is the answer is in your question. Less people use node.js and rails, and django, so less providers are going to support it. Wide support = wide usage (im assuming)