Why does the CMP not delete existing cookies?
Lets assume the visitor goes to a website and clicks on accept. He will then receive some cookies into his browser. Later the visitor reopens the settings and clicks on reject. The CMP will in this case not delete any existing cookie.
Deleting cookies later is technically only possible to a limited extent (only possible for first party cookies, not for everyone else) and does not make much sense from a data protection perspective: If the user rejects, the CMP will block the third-party codes on your website. This means that the cookies are neither read / written by the third-party provider nor processed in any other way. The cookie is thus a "dead" file on the user's computer that has no function. In this sense, it is not necessary to delete the cookie.