[sixdimensional]

I don't know about the OP's reasons, but one of mine lately has simply been dependency management and simplicity of deployment. It's just handy to be able to package it all together, especially for packaged software where deploying another component would be more configuration. I suppose this is why docker containers (or in the past, virtual appliances/VMs) have become so much more popular.

The good embeddable web servers are usually pretty lightweight, scalable and can be programmatically configured. Things like Jetty are popular, but look at languages like Go that have HTTP serving built in via libraries and scale nicely via coroutines.

Vert.x etc. are cool for performance reasons, being lightweight and usually much less thread hungry (using async operations, sometimes in many less threads).

That said, I do agree that reverse proxies are still really useful for all the reasons you mentioned. Reverse proxies on top of some of these high performing embedded HTTP serving engines is a good practice, when you need it.

And there is no need to throw out the tried and true engines, like Apache, Nginx, etc.

Just depends on the use case and needs I suppose.