Lately I've occasionally been running into round check boxes that look like radio buttons. Why????

UX want to put their own spin on things. I’ve noticed this repeatedly.

UX has gotten from something with a cause to being the cause for something

In 20 years of front-end web development I've never encountered a designer willing to use standard form controls. I assume they exist.

I think the answer is they just don't know.

iOS decided square checkboxes were ugly, and design patterns are flowing from mobile->desktop these days.

I think Apple does stuff like this because a) they can get away with it and b) they know countless competitors who can't get away with it will blindly follow their shitty new design paradigm.

And yet, Microsoft is still doing their own thing. It's a shame they didn't follow through with, and / or the industry didn't follow along with, Windows Phone because it was a pretty unique design.

Google / Material Design also does their own thing still.