"Why don't the people of Gotham just move?"
Because it's a massive East Coast city but the property values are probably like $200 a month for a three bedroom apartment, and most Gothamites are like, "Hey, Bane never swore to break my back."
And here's the thing: you're not just moving out of Gotham City. You're moving into the rest of the DC universe. And it has hero-based power scaling.
Oh, Metropolis looks fucking great. But it gets invaded by aliens and robots and demigods, because Superman is there.
Wonder Woman's tangling with gods.
You go to Central City, and some Reverse-Flash motherfucker runs backwards from an alternate future and kicks your balls off at the speed of light.
You could move to the West Coast, and oh, an entire city just gets exploded by Cyborg Superman or some shit.
How about you move to Indianapolis, or Cleveland? Haha, no. They have no protector during the alien invasions, and you're in Cleveland
So stay in Gotham. Sure, you have lunatics, but you know that if you had a gun, you at least have a chance against the Joker or Riddler. Mongo of War-World would crush you. But Gotham just has creeps, and you know you have a chance. Even Bane, R'as Al-Ghul, Killer Croc, and Mr. Freeze are just slightly altered dudes. Oh no, Poison Ivy is going to kiss me to death! Who gives a shit, you kinda wanted to go out that way anyway.
There are super-intelligent telepathic gorilla warlords in Africa and the Greek titans are real and chained in the abyss
This does beg the question of why Gotham has such a horrible in-universe reputation when all its villains are relatively human compared to the cosmic bullshit that most other heroes put up with.
I think it's all about perception. Gotham City has crime. But when Ares sends his undying legions to march upon the mortal realm and Wonder Woman has to punch all of them, people don't internalize that as "crime." That's "a crisis" or "a religious event" or at best, terrorism. Same thing when Superman has to stop Brainiac from shrinking Metropolis or whatever. That stuff is objectively more dangerous but it's on such a huge scale that "crime" is not the word for it. The cops don't involve themselves in this at any point. But the stuff Batman deals with is like, robberies, assaults, gang wars, serial killings. All his villains commit actual crimes, so they go into police reports, which end up as statistics. So when someone compiles all this data, oh look, Gotham City has the highest crime rate in the country, yet again. Forget the fact that 10% of Keystone City's population had their skulls crushed by invading superintelligent gorillas. Who cares that a random guy in Opal City accidentally teleported the entire state to Hell after he found out the hard way that he was born a wizard. Those are not crimes. There's nothing in the police recordkeeping app's drop-down menu for a Gorilla invasion. Closest thing we've got is Random Chimp Event.
So my theory is that while Gotham does have a lot of crime, what it does not have is space catastrophes. And so it ends up being the most dangerous city based on a bureaucratic technicality.
all this is very true, I just wanted to point out that the worst thing about metropolis isn't the alien invasions, killer robots or meta human fights breaking buildings, it's the power hungry scheming ego maniac billionaire who gets enough of a pass from the population, despite the several journalistic exposes about him, that he's been able to run for president and win
at least gotham's billionaire is funny in the tabloids and, even if he's rather ditzy, he seems to be helpful to legit causes, against all odds
