I agree with fny's comment, and add that most "application servers" don't bother with things like supporting sendfile(2); e.g. when hosting a Python application, you need to add something like Whitenoise, and integrate it with your application somehow; that's extra development work that is sometimes easier to throw over the fence at the sysadmin (especially since the sysadmin will usually already have that part of their job automated).

I'd also say that there is no such thing as a "general case"; I've launched and/or supported countless (must be hundreds?) of web projects and even the "simple" ones were each a bit of a snowflake.

https://man7.org/linux/man-pages/man2/sendfile.2.html

https://whitenoise.readthedocs.io/

But that is the general case. Most web apps are written in interpreted languages like JavaScript which benefit from a reverse proxy. If I remember correctly, NGINX became popular because of Rails.

Maybe in Java-land it’s overused, but everywhere else it makes sense.