> * I have yet to see this kind of universal support for any other language than PHP. Not even Ruby on Rails, let alone Java, is available on mainstream providers, thereby validating the claim I made five years ago that Ruby on Rails won’t become mainstream (I regularly receive emails about this article asking me this question, and I keep responding “Nope, still not mainstream”).*
If your provider doesn't support Ruby, you need to get yourself a $20/month Linode box. If Linode and a $20/month price point isn't mainstream, I don't know what is.
I have a friend with a webcomic and an art gallery page. She doesn't need ruby on rails and a 20 dollar a month host. PHP is a nice solution for her.
That's why PHP is still around.
I'm using a fairly "non-noob" ISP (ssh access, crontab, etc...) and they still don't give me access to much more than PHP. I can install Java but I can't even run it as a CGI because of the HTTP request memory constraints they impose. This is pretty standard, I don't blame them for doing this, and I would go with a VPS if actually needed all this.
Same for Ruby on Rails, obviously.
To my downvoter, here's a list of "mainstream" providers, at the Godaddy-level, and language support:
Dreamhost: RoR, PHP, Perl, Python 
Godaddy @ $8/month: PHP, Perl, Python, RoR 
a2Hosting @ $3/month: PHP, Perl, Ruby, Python
That seems pretty mainstream to me.
I work for an ISP and in about three years nobody had asked us about anything¹ more complicated than a simple PHP hosting with FTP access. (We don't really advertise hosting solutions, though, as this is not our main business.)
If you want your ISP to support something like Java or Rails — ask them today. They probably won't offer it now (or - who knows - they may surprise you!), but unless they're a type of company where individual client feedback gets lost, they'll note your request.
¹) Except for a colocated hosting, to be precise. But that's completely another case.
True. And if nothing else, you can run Python on Google App Engine for free.