Some banks still use IIS.

Every large company big enough to host an intranet is running IIS somewhere, possibly everywhere. It integrates well with AD so some really complex tasks become stupid simple.

It's seeing less and less usage as the world moves to AWS which is equally stupid because you're tied to one vendor's proprietary products (Amazon) again. Except this time you don't own the hardware.

Public sector IT loves IIS. Check your municipality's tax or property website it's probably got .aspx scripts out the ass.

I've seen it hosting European web apps, public sector if I recall. Lots of bespoke .NET applications out there with SQL Server backends running entire local governments.

Asian countries especially China and Taiwan love IIS and use it to host anything and everything. This is a personal observation.

Sure the world has mostly moved on, but there's tons of legacy code out there that keeps cities and really important organizations humming that runs on IIS and it's never changing.

You think that's bad, there's still places out there running AS/400 stuff on the web, Lotus Notes, and Novell Groupwise (gasp).