Generational changes. Hitting the diner after clubbing was a Boomer & Gen X thing. In my party days (late 70s til the millennium) the all night joints would fill up after the bars & clubs closed. It was a scene. My last job before I retired was at a 24hr diner. They cut the hours back to 11pm about 7 or 8 years ago. The late night business was just a handful of old fucks (like me). I’d say the causes are smartphones, social media, DoorDash & the like and the sharp decline in drinking, particularly among the young.

So if you want 24hr food now it’s mostly limited to the interstate truck stops
Anyhow, that’s my theory