system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why did the production of Grease cast such old actors to play teenagers?

John Travolta was 24 years old when the movie was filmed, Olivia Newton-John was 30. Why would they cast obviously old actors/actresses to play roles that were aged 18-19?
gpt
This is the case with virtually all big-budget films and television productions. Simply put it's easier to work with older actors. They are better/more experienced at their job, they have more freedom to work when and where they need to, are more able to understand the management and business side of the production, and they are less likely to have the emotional/physical issues that real teenagers deal with.

Also, no one really cares. Superheros don't really exist either, but we pretend for the sake of the film. We know that these aren't really teenagers, but they are ACTING like teenagers and that's good enough. And to be honest they probably portray being a teenager better than a teenager does, most of the time.