Because when you're just some guy that wants an answer to the question "how do I get some things from a database into a web page", the answer that starts "Well first go set up a VPS..." and hits "There's this thing called MVC" somewhere in the middle is not something someone who just wants to put a list of things into a web page is going to listen to.

Then a month later that guy that pulled those couple things into a web page is going to go "Hey, maybe I could make a thing to manage those.". And he's going to learn more.

Then a month later he's going to have another bright idea.

And suddenly someone with no programming background is a PHP programmer, and he's putting together ugly but functional websites and everyone is looking and going "MAN PHP IS AN AWFUL LANGUAGE".

There's a huge contingent of people that are maybe moderately technically savvy but are not programmers and are not necessarily interested in deliberately becoming one. These are the people that end up setting up entire businesses in some Lovecraftian Excel sheet. PHP is a language with a learning curve (even for a non-programmer), not a learning cliff, and it makes it really easy for these people.