They're not going to put their name on it if they do.

Until fairly recently "jingles" - ad music - were a huge source of income for many musicians with full time careers. Likewise library music, which was prerecorded with a specific mood so music editors could drop into their projects without having to commission it, and then the composers would be paid for performance royalties/residuals.

Writers - not such a thing now, but in the 60s and 70s a surprising number of "serious" writers in the UK began their careers writing ad copy.

Famous movie directors - many started in the ad slop trenches.

Music videos are literally ads, and it's not a surprise they use many of the same techniques and are directed by ad industry people.

And then in tech there's ad tech...

AI is just the newest arrival to the party.