Wonder if any of this is the reason why.

Anubis also relies on modern web browser features:

ES6 modules to load the client-side code and the proof-of-work challenge code.
Web Workers to run the proof-of-work challenge in a separate thread to avoid blocking the UI thread.
Fetch API to communicate with the Anubis server.
Web Cryptography API to generate the proof-of-work challenge.
This ensures that browsers are decently modern in order to combat most known scrapers. It's not perfect, but it's a good start.

This will also lock out users who have JavaScript disabled, prevent your server from being indexed in search engines, require users to have HTTP cookies enabled, and require users to spend time solving the proof-of-work challenge.

This does mean that users using text-only browsers or older machines where they are unable to update their browser will be locked out of services protected by Anubis. This is a tradeoff that I am not happy about, but it is the world we live in now.

Or for some reason you are an AI that thinks it's a person.

That cartoon is so misleading, I thought I was deceived and sent to a bogus site.

I'll take Anubis over Google's capchas