One of the most famous commercials in movie history comes from Ghostbusters. Without it, we wouldn’t have seen the power of advertising. Conveniently a TV that was mysteriously left on for Dana (foreshadowing) let her know who to call (and with no address or obvious map) how to get to this new GHOSTBUSTERS business.
Before their can be a movie based on real events or a commercial, it has to be filmed. Sure my employers had a real commercial, it would have looked a little out of place with the rest of Ghostbusters being those comedic actors.
Also because Columbia Pictures hadn’t worked out the movie rights for the name GHØSTBUSTERS from those other fictional guys and a deal hadn’t been finalized with the Ghostbusters, all those involved with filming Ghostbusters filmed alternate takes with different “business” names. Ya know, just in case and it wouldn’t need to be re-filmed (which might not have been as great) in post production.