When it was announced that Keaton would return as his iteration of Batman in Batgirl, fans were ecstatic to know he was coming back. There may have been some extra incentive on Keaton's part because returning when superhero movies reign supreme meant good money was coming his way.
Keaton is considered an OG superhero icon because of his casting as the original film version of Batman back in 1989, which was around the time superhero movies were beginning to make their way into Hollywood. With the superhero genre as popular as it is, Keaton's return as Batman for Batgirl got him a nice payday. The cherry on top of all that is that he was paid a grandiose amount for little screen time.
In an article written by The Hollywood Reporter, it was confirmed that most actors these days turn to superhero movies because that's where the money is these days. In this article, they confirmed how much Keaton had made from appearing in Batgirl though the film would be cancelled. "Keaton received $2 million for Batgirl, the $90 million film that Warner Bros. Discovery ultimately shelved, after participating in about a week’s worth of work, described by sources as a glorified cameo." THR then added that, much like other actors, Keaton did it because returning to play Batman again is easy money for him. "For Keaton, donning the Batsuit may be the closest a star can get to living like Bruce Wayne."
It's amazing how far Keaton has come in the eyes of superhero movie fans. Originally they were opposed to having a comedic actor like Keaton take the reins as a live-action Batman back in the 1980s, but once he took the screen as the Caped Crusader, their minds were changed instantly. Because cinematic universes weren't a thing back then, when an actor dropped out of a project, the studios simply replaced them. Now, studios want actors to play the role as long as they can because of cinematic universes, so to see someone play the role again all these years later adds some sentimental value to it.
Regarding Keaton's would-have-been Batman cameo, it's not even just that superhero films are all the rage until further notice. It's the nostalgia factor behind these scenarios. Nostalgia has been just as prominent in Hollywood as superhero movies are nowadays, which had led to reboots and revivals galore. When those two elements are combined in this generation, it makes for one financially profitable movie. Fanboys were excited enough to see Tobey Maguire and Andrew Garfield return in Spider-Man: No Way Home, which is why the film made as much money as it did and even made a return to theaters early in 2022. Naturally, studios will try to utilize the nostalgia element in superhero media as much as possible now that they know fans will come to see it.
Luckily for those hardcore DC fans, Keaton is slated to make Batman cameos in multiple DC films over the next few years, including Ezra Miller's The Flash, and there's no telling if it'll stop there. For all we know, that may lead to more cameos like Chris O'Donnell returning as Robin in the next year or so. Now that Hollywood knows superhero movies combined with nostalgia will put butts in those seats, they are going to milk that as much as they can.
Batman can currently be watched on HBO Max
Source: The Hollywood Reporter