Of course, there is pythonanywhere or you might want to use PAAS like Heroku, but I find it interesting non the less. Is it so much more work for shared hosting providers to provide Python?
That said, isn't 'IaaS' like Heroku basically 'shared hosting for other stuff'?
Rewind to 2005: Django and Rails had just been released. PHP had already been out for 10 years and there were dozens of large systems - PostNuke, phpBB, WordPress, Drupal - that were already out there being useful.
For many hosts, their customers wanted to get a blog, forum, etc online quickly and easily. The vast majority were written in PHP, so they set up with PHP by default. Throw in the fact that most of these companies deployed Cpanel (or similar) with one-click installers like Fantastico, etc - which dealt with PHP exclusively iirc - and it was a no-brainer.
The availability of apps drove PHP deployments.
The sheer number of PHP deployments drove the installation of the same apps.
It's easy. Compare with trying to track Rails upstream, particularly in the 2.x/3.x days when minor version increments could sometimes see you building a whole new set of ruby binaries compare to what shipped with your base Linux distro.
How often do you hear PHPers handwringing about virtual environments, locking dependencies, and whatnot? Like DOS and Windows, the PHP world has done a pretty good job of making it easy to install PHP, run PHP programs, and not spend hours of your life dinking with mutually-incompatible bits of the stack.
Why would a shared hosting service want the pain of other solutions?
PHP was designed from the ground up to work well on shared hosting with things like restrictions on CPU and memory use so one user wouldn't bring down the others. Here's PHP's inventor explaining:
The simple answer is that the last time I looked I couldn't find good documentation for getting Python (and Ruby) support working side-by-side with a modern LAMP stack. Most Python (and Ruby) hosting-related documentation assumed nginx, which, while I like it otherwise, still lacked good support for .htaccess files, which are a must-have when providing hosting for people using things like Wordpress and Joomla and Drupal. The documentation that I could find for Apache environments was way, way behind the best practices for a PHP+Apache environment and some of the recommendations were orthogonal to my current environment.
I still would like to provide a hosting environment that can handle a mix of PHP and Python and Ruby, but it's going to be fiddly and involve a lot of trial-and-error and I haven't been able to justify the time sink yet.
Getting suexec + event-mpm + fcgid + PHP opcode caching has been enough of a headache as it is.