Comment by thayne

I was involved in evaluating captcha solutions. The only recaptcha alternative that met the requirements that we were able to find has hcaptcha, but it wasn't any cheaper (for us), and would require going through the vendor approval process, whereas google was already an approved vendor. There wasn't really a compelling reason to switch.

Maybe there is a better option out there, but if so, it has the disadvantage of being hard to find.