Showing the seedy underbelly of places is a great way to set a mood and demonstrate to the players that this is a real, gritty place, where wealth and prosperity are built on a foundation of lower classes and suffering. Some types of games typically tend to gloss over this sort of stuff - for example the typical pseudo-medieval fantasy world where the peasants are all well-fed and happy, or simply never referred to.
If your players are comfortable in the illusion that there is no lower class suffering in your campaign setting, putting it front and centre can be a way to shock their worldview and inspire new types of adventures.
Commentary by memnarch (who has not seen the movie)
Oooooookay? Yet again, not where I would have expected the story to go. Definitely playing up the "this casino is just a shiny lights and sound show" angle. Maybe Rose and Finn are here to rob the place for something? The scene would help the audience feel better about having the place robbed as well. Or blown up. I could also see the casino getting blown up as part of an escape.
The lighting from the lightning on the four-armed alien helps sell the idea that the people in charge suck. That face looks like a pile of ground beef on gravel! And while judging people by their appearances isn't good, it's definitely something that comes up frequently anyway, even when not paired with animal cruelty.
Also? Wow, that's a heck of a callback. And here I was trying to remember what other campaigns or movies that could have been referring to before I recalled specifically Annie's previous characters prior to Finn.
GM: You notice a four-armed alien trainer cruelly whipping another fathier in the infield.
Rose: A painful place to be whipped.
GM: A young human stablehand tries to intervene.
GM: The alien knocks the boy down and threatens him with the electrowhip.
GM: Two other children rush to protect the stablehand.
Oniho Zaya: You okay, Temiri?
Finn: Do we need to see animal cruelty and child abuse?
Rose: He’s showing the seedy underbelly of this glamorous casino, so we don’t feel morally conflicted about robbing the place.
Finn: Taking their money isn’t going to stop the maltreatment. Can we help them?
Rose: I don’t know. We didn’t actually come here to free slaves.
Rose: Look what happened last time we did that...