Ads Like This...
...Were part of the "contract system" practised by Hollywood in its glory years. As part of their seven-year contracts with major studios like Warner Bros. (Reagan's studio at the time), actors were required to appear in whatever advertising the studio wished to put them in. There was no "out" whatsoever; if the studio had made you available to an ad agency for a product endorsement, you were required to pose, by contract, and your name appeared as an endorsement of the product, whether you used the product, liked the product, or not. The fees paid by ad agencies for stars to appear in ads represented a healthy subsidiary stream of revenue for studios. Actors might or might not be paid something for this use of their names and images, according to how big a star they were and how successful their agent had been negotiating their most recent contract. As much as we long for the good old days of Hollywood, stars were essentially owned by their studios, told what movies to make, what ads to appear in, what marriages were good for business and what marriages were not - everything about the star's life was regulated by contract. It was an existence not too far removed from slavery, even if it was financially well-rewarded (Bette Davis was the highest-paid individual in the United States for a year or two there).
So, don't think that Little Ronnie Reagan (Bette's derisive term for an actor she considered a lightweight) actually liked Chesterfields, or that Claudette Colbert actually used Lux, or that Kim Novak really had a Simmons Beautyrest or an Edsel - all these ads were their studio's doing.
P.S.: One of the funniest studio ad placements ever happened in the 1940s - Joan Crawford for Royal Crown (R.C.) Cola, ads she was required to do under her Warner Bros. contract. As we all know, once Joan broke away from studio contracts to become a free-lancer in the 1950s, she rather fervently endorsed another cola brand, preferably with a shot of 100-proof Smirnoff in it.