Don't get me wrong -- passenger is great. But it's not set up by default (or even possible to set up often) on most shared hosts. Heroku is cool, but as a freelance developer I've found that it's best for me to not take any responsibility whatsoever for the hosting side of things -- just leads to the most un-fun kind of responsibility down the road.

Also, we're mostly programmers here, but there are a vast number of websites created by designers who have very limited understanding of programming and hosting setups, and all they know is shared hosting, copying files via ftp, and setting up wordpress (and maybe creating a database in phpMyAdmin).

Speaking of wordpress, that reminds me of the #2 reason for PHP's continued popularity despite its arguable sucktitude: applications! See http://www.codinghorror.com/blog/2008/05/php-sucks-but-it-do...