The simplicity of it is logic defying. It used to be that you had to find crosswalks or move puzzle pieces or type blurred letters and numbers, but NOW all the sudden I can just click a box and HEY!, I'm human?
That's hardly the Turing Test I'd expected.
I used to think it was timing based, but now leaning on the idea that it just performs more fingerprinting in the background: user agent per ip pool, canvas or puppeteer checks.