I hate that joker is kept around in the Batman comics. I swear, he's only kept around because of the meta, not because he's a great character. Personally, the only time I really liked this modern take on joker, was Arkham City, and that game is over a decade old (2011). Heath ledger did a good job with his role, but modern joker is not built for multiple appearances. Maybe back during the comics where he was actually more clown like, and he wasn't known for killing an ungodly number of people, it made sense to keep bringing him back, but modern joker is too irredeemable to justify his ongoing existence in-universe. In any even slightly sane world, joker would have been executed by the court, but somehow, that hasn't occured. Heck, even in the DC universe, surely SOME vigilante would have gotten pissed enough and definitively killed him. Any sane writer for a Jason Todd (the Robin joker killed, but came back to life decades later and is a really cool character) story would have had a great long storyline that would have ended with the death of the joker for good. The only time joker ever seems to die is in elseworld stories, and even then, it (stupidly) always seems to lead to ruin, with injustice being a prime example of this bullshit. I get where batman's no kill rule is coming from, but how does everything else seem to fail to stop the joker?
Tldr; joker isn't kept around because he's a good character, he's kept around because he brings in the money.
What makes the joker funny is other characters
There are a lot of jokes about his complete lack of concern for his henchmen and Harley Quin
When he effects other people with behavior effecting chemical weapons they become funny
When he forced someone to agree to do him a favor in order to live and called him years later that person played a funny joke on the joker
Without these other characters the joker would be much less funny
That might be why he needs batman to live
Also the joker has joker toxin so if anyone kills the joker then they become the joker
Although if people knew that they could execute the joker in a room which is sealed so that the joker toxin does not leave
Although being exposed to joker toxin might not make someone evil because the creeper got exposed to joker toxin and did not turn out any more evil than Freakazoid
There are actually multiple jokers at the same time in some of the comics
So they might argue that you can not get rid of the joker because of joker toxin and joker's from parellel universes
But they do not like eliminating such well known characters pertmanently because then they would have to write new characters
And comic writers change teams so if the joker was actually eliminated but another writer liked the joker they would just make him alive again in a new comic
They could have better security but then they could not make new episodes
In real life they could male it very much unlike!y for the joker to escape and give him a life sentence but they have to increase the likelihood of him to escape so they can write new episodes with him
So supposedly batman killed people in the early batman but they wanted to make it more acceptable to parents for kids to watch and created a no kill rule
But in a bunch of comics not in the standard universe there are versions of batman that kill people
Now not only is the joker difficult to get rid of because hevis so famous but also copycat jokers are created like punchline and other joker fans who try to imitate the joker in the comics
And by the batman beyond timeline there is a whole very large very violent joker copycat biker gang who is usually not even depicted making jokes or there jokes are so subtle that I usually miss them
Here is another angle to look at it from
What if the joker is not supposed to be funny but he is evil because he wants to force people to acknowlefge him as the funniest person in the world and is willing to do evil things to force people to act like he is funny
@TrueMasterCole
Basicly the joker is too famous at this point to get rid of because even if most people did not like the character as long as someone does like the character there will be an audience and there will be people who want to write stories about the joker
A small percent of a large number can be another large number
If 300 million people heard of a character but only 1% like that character enough to buy stuff then that is still a audience of 3 million people that will buy stuff