Rails And PHP Are The Access(es) Of The Web
There are two issues: one is the ease with which a person with some knowledge can solve some (relatively simple) task (the classic "build a doghouse" project). If I want to build a doghouse on the Web, I'll do it in Ruby on Rails (in part because I always want the option of evolving it into a more sophisticated structure).
The other issue is the bridge between power-users and programmers. Although I suspect that most people with an interest in computers would "get" Python or Ruby and might be intrigued enough to learn how to build doghouses, I think that the reality is that PHP has become the dominant bridge -- it's the Basic, dBase, VB, Access, etc. of the Web. Almost every resume from young programmers I've seen in the past few years includes some reference to PHP.
For almost 50 years we've seen programming languages succeed and fail. But no one talks about the lessons to be learned from that. Everyone just wants to walk through the carnival, gaping at the pretty lights and giving up their money to the hucksters.