Why can't you set up Nginx + Ruby On Rails without Passenger?

Question

Nginx

Subject. The whole point of the issue.
What can't be made to work RoR + Nginx without Passenger??
After all, the same Php does not require any dregs for this.
But Django like Gunicorn requires it.
Our admins always do this, and I did not delve into these issues.
Now for the general development I decided to read. And I stumbled upon it ;)

Answer 1

Because Nginx does not know how to execute dynamic PHP/Ruby/Python/etc scripts out of the box. Nginx is well suited for serving static files and proxying. To make it work, for example, PHP is additionally installed with another web server (for example, Apache + mod_php) or other tools (for example, PHP-FPM), while Nginx is configured for proxying. It's pretty much the same with Ruby/Python. That is, Passenger in this case is needed for Ruby applications.