CAPTCHA appears on the user’s third attempt to submit a form from the same IP address in a short period of time. It might also appear on the first attempt if the enhanced anti-spam protection is enabled.
Normally, CAPTCHA is not shown to regular users (those who are not bots). Unfortunately, you cannot disable CAPTCHA, otherwise, you will be receiving a lot of spam via the form.
If the website requires checking the box “I’m not a robot”, but it does not appear on the screen, try to disable third-party extensions in your browser that can block the display, for example, Adblock, uBlock, Ghostery, and others.