Some provide screen-reader instructions, but most places barely remember blind people exist. It’s another example of people with disabilities being ignored and marginalised.
And then even if they do remember blind people exist, they probably forget there are people who aren’t blind who can’t do their tests for other reasons, like dyslexia or dexterity impairments.
And then you have hCaptcha who makes disabled people to sign up to their database to use their cookie.