I am genuinely curious, to those still building SOAP based APIs in 2022, why??

Because the vendor is from the Stone Age and doesn't know wtf a rest api is.

Plus, using an XSD for validating api data isn't a bad thing.

Jolly torturing of devs, why else?

envelope signature could be one of the reasons IMO

Because the api standard for connecting brokers to insurance company systems for our country defines SOAP.
And our team is tasked to write an service to provide such an endpoint and connect it to our internal system.
Also, that standard has errors and inconsistencies.

Upnp has is the only api my router understands.

I would say Dove maybe?

They could build a soap API.

GET /ingredients

["aqua", "stearic acid", "lauric acid", "sodium palmate", ...]

The reason is nostalgia. I really want to build something on PHP 5.4 and Apache in 2022, just because it brings me back in time when I was a student, the world was simpler, there was no war between my country and Ukraine, and I actually remembered what an integral equation is and how to solve them.