Captcha usability

Web programmer note.

Quite often captcha is used when filling out the form. And again, very often, if the user correctly entered the “secret code”, but incorrectly entered something into other form fields, the form is shown to him again (with an indication of something which is not correct) and ... the captcha is shown again. What for? After all, the user has already proved that he is not a bot.
On the technical side, it’s elementary to do so in order not to display a confirmation code in the second, third or hundredth time, provided, of course, that it was entered correctly the first time.
So why lazy and irritate users once again? :)