Looks like they provide an appropriate alternative for people with vision disabilities: https://support.google.com/recaptcha/answer/6175971?hl=en

That only really leaves blind deaf people out, at which point we might be reaching the limits of any technology to provide access to everyone without a tooooon of work.

As someone already pointed out in another reply, you don't get this option if you score low enough.

Yeah but most people won't trigger that. Seems like most of the complaints here about triggering it often are from people who are blocking js/cookies/randomizing user strings. The NoCaptcha check box itself is better than the old system where everyone had to do the Captcha at least.