Because modern web apps are more than just a thin layer over the database. Here's my recent experience: 1. An image server cobbled together using RabbitMQ, Op

Because modern web apps are more than just a thin layer over the database. Here's my recent experience: 1. An image server cobbled together using RabbitMQ, OpenCV, and Imagemagick. ElasticSearch is used for title/description searches. Sure this could technically be done in PHP, but 80% of the code has nothign to do with the web in particular so its better to use a general purpose language that was designed from the start to be that rather than PHP which was a domain specific language that evolved to where it is today. 2. Hedge fund manager using Quantlib and NumPy. There's no equivilent in PHP. There's no easy way to interface with C-code. Cython and Cytpes make it easy. Doing so in PHP means hand writing a C-extension. I've done that before and let me tell you the Zend Engine not a pretty thing to work with. 3. Any project that has a rich client side interface built in javascript will get gains from using Python over PHP. At that point your server is really just a message backend controlled via REST or JSON-RPC.