A lot of time (most?) writing software isn't about writing software for the pleasure of doing so, but for building something that helps generate revenue.

For businesses, having a highly optimized web application that takes a long time to develop and doesn't allow for quick additions of new features is not worth the cost. Instead, they can have a poorly optimized web application with way more features and a faster feature production because Python/Ruby/Javascript are more approachable than other native languages.