If you sit down at a randomly chosen web server and write two files, one ending in .php and one ending in .rhtml, which file do you think has the better chance of working correctly? Newbies would prefer not to know what CGI means, let alone how to edit an Apache setup file.
But, yeah, PHP is a scary language. In addition to what you've already mentioned, PHP's core "array" datatype appears to have been designed by a committee of drunken camels.
I would not expect someone trying to learn to program to select a web server to test projects on randomly. Installing mod_ruby is as easy as installing mod_php. Finding web hosts that support it isn't hard either.
Plus, there are Ruby on Rails packages that don't even require apache! You just download the package, install it, then you can run a built-in development webserver by typing "script/server". What could be easier?
(OK, I know of one stealth mode startup that's going to make it even easier, but that's beside the point.)
But, yeah, PHP is a scary language. In addition to what you've already mentioned, PHP's core "array" datatype appears to have been designed by a committee of drunken camels.