At the time is was useful, as the Mac desktop was my daily driver. Unfortunately current macOS versions are really sluggish, so its currently a home "server" running Fedora 31.
The 16GB RAM limit is becoming a bit of a problem, so I will likely replace it with an Intel NUC.
First, even though there were quite a few decent-sized Mac Mini deployments like you're describing, I'd be genuinely surprised if that accounted for a decent chunk of Mini sales overall. Some, sure! But most? I wouldn't expect it.
Second, does any of that require running Server? We have a database and application server in the office here, but it's not running Server: it's just plain macOS running daemon processes.
Why would people buy that over the iMac for daily use?
Also, I bought a Mini for my desktop because it's tiny, cheap, and powerful, and I can use my own screens.