Here are some valid reasons:
1) Because Batman's universe has a rich amount of lore/worldbuilding, strong character writing, and great stories. There is a reason why BTAS is constantly brought up as not only one of the best cartoons of all time but also one of the best shows of all time.
2) Batman Beyond, Suicide Squad (animated movie and second live action movie), Harley Quinn, Joker (first movie), and other properties out there have proven a show/movie can not only be carried by people other than Bruce Wayne, but they can actually thrive and be successful by doing so.
3) Because the Batman Universe is a money-making machine for WB, moreso than any of the other properties you've listed or a new IP.
The only crazy thing here is that this show is as good as it is and that's all without dumb forced cameos from Batman, because it means that maybe the suits at WB are finally starting to take their collective foot off of the neck of creatives there who just want to tell a really good story.
Most of that stuff is still superhero focused, which is fine. I'd argue the Joker film is a rare example of something really benefitting from a batman association that wasn't necessary.
But a GOOD show doesn't need Batman. It's BATMAN that props up BAD SHOWS because then at east you get some Batman! Take that comedy show from a few years back with Alan Tudyk as "Bruce Waynes Cousin" where they make all the tech or whatever. It was juuuuust Batman focused enough to push the show over for me, but since it was still heavily superhero focused I don't think it needed Batman specifically, they could have made up their own superheroes.
But if I am going to do a CRIME show, I don't see the point in setting it in and around Batman if frikken BATMAN isn't gonna show up! Gotham didn't need it. The memberberry aspect of "oh oh, is that guy gonna be the Joker!?!" just cripples the show I think.
Imagine if The Sopranos was "The Penguins" instead, or The Wire was "Gotham Beat". Any value added there? Or just handicaps?
If you are going to do a genre cop/crime show (if The Penguin has any of that stuff in it, don't know) then there are LOTS of other IPs out there. Hell, buy up "Forever Knight" or "The Desden Files" for a song and go nuts!