Some good answers in here already. It boils down to a couple points for me:

• Back when I started selfhosting, it was either nginx or apache, and I found nginx better and easier to set up
• All the nginx knowledge I learned years ago still works just the same as it did back then, so why potentially mess things up by switching if it all still works
• Basically every project has an example nginx config for reference, that can’t be said about other proxies
• It is easier to find support online for edge cases that might pop up with nginx due to the ubiquity of its use and years of history

Because Nginx Proxy Manager exists.

And also because for me it started from web hosting where Apache and Nginx dominate and later because of many easy to understand example configs from the net including many “docker letsencrypt” examples.

TLDR: probably a lot of people continue using the thing that they know if it just works as long as it works well enough not to be a bother.

Many many years ago when I learned, I think the only ones I found were Apache and IIS. I had a Mac at the time which came pre installed with Apache2, so I learned Apache2 and got okay at it. While by release dates Nginx and HAProxy most definitely existed, I don’t think I came across either in my research. I don’t have any notes from the time because I didn’t take any because I was in high school.

When I started Linux things, I kept using Apache for a while because I knew it. Found Nginx, learned it in a snap because the config is more natural language and hierarchical than Apache’s XMLish monstrosity. Then for the next decade I kept using Nginx whenever I needed a webserver fast because I knew it would work with minimal tinkering.

Now, as of a few years ago, I knew that haproxy, caddy, and traefik all existed. I even tried out Caddy on my homelab reverse proxy server (which has about a dozen applications routed through it), and the first few sites were easy - just let the auto-LetsEncrypt do its job - but once I got to the sites that needed manual TLS (I have both an internal CA and utilize Cloudflare’ origin HTTPS cert), and other special config, Caddy started becoming as cumbersome as my Nginx conf.d directory. At the time, I also didn’t have a way to get software updates easily on my then-CentOS 7 server, so Caddy was okay-enough, but it was back to Nginx with me because it was comparatively easier to manage.

HAProxy is something I’ve added to my repertoire more recently. It took me quite a while and lots of trial and error to figure out the config syntax which is quite different from anything I’d used before (except maybe kinda like Squid, which I had learned not a year prior…), but once it clicked, it clicked. Now I have an internal high availability (+keepalived) load balancer than can handle so many backend servers and do wildcard TLS termination and validate backend TLS certs. I even got LDAP and LDAPS load balancing to AD working on that for services like Gitea that don’t behave well when there’s more than one LDAPS backend server.

So, at some point I’ll get around to converting that everything reverse proxy to HAProxy. But I’ll probably need to deploy another VM or two because the existing one also has a static web server and I’ve been meaning to break up that server’s roles anyways (long ago, it was my everything server before I used VMs).

Nginx “just works™” had never got into the way, its been rock solid and has not changed significantly over the years.

Why would I need something else?

It’s pretty good, innit?

There’s a lot of good resources for Nginx, it’s fast (faster than Caddy), and has a ton of features, so you can use it for pretty much anything HAProxy, Apache, or Caddy can do, and not sacrifice much in performance.

That said, I mostly use HAProxy and Caddy. Here’s my basic setup:

1. HAProxy at the edge VPS - routes requests to machines based on SNI
2. WireGuard VPN - connects my internal devices to my VPS
3. Caddy in Docker - runs on internal network on my NAS/homelab - manages LetsEncrypt renewals and reverse proxies to internal Docker network
4. Nginx in Docker - FE for NextCloud; this simplifies things so all my TLS is handled in one place, and Caddy doesn’t need to touch files

I use a local DNS server on my router so my domains can route directly to Caddy instead of going over the internet when on my network, otherwise I may just have HAProxy handle LetsEncrypt certificates.

From what I can tell, Nginx is a little more efficient than Caddy, but Caddy is plenty fast for my needs. I’m considering switching from NextCloud to the new ownCloud Infinite Scale, and if I do, I’d ditch nginx completely.

I think a lot of people just haven’t heard of Caddy. Since I’ve found it I haven’t used anything else.

Back when Nginx started, Apache was the only alternative and a big pain in the ass. That’s how it became popular.