When restaurants shut down, why isn't it more common for them to publish their recipes?

Half the time it would just be a Sysco product list.

Biggest surprise in when I worked in restaurants in college was how all three "fancy restaurants" ordered the same type of soups from Sysco. Chefs did spice it up differently.
Or the units of measurement would be "half of big pot"

Why would they? It's takes work with no return. It's giving something of value (theoretically) for nothing in return, not even good relations for the restaurant since they are now gone.

I worked at a pizza place that shut down, and it never even occurred to anyone. For one thing the owner was obviously stressed out worrying about a bunch of other things, both in the restaurant and in her personal life, and you'd be surprised how much of the food you get at restaurants is really just purchased from a company like Cisco and warmed up for you. We did make the actual pizza from scratch though, and that place had the best crust of any pizza place I've ever been too. The problem there was that the recipe was very simple. Just flour, water, oil, salt, sugar, and yeast. That's it. The trick is the exact ratio, and a proper pizza oven. The oven a recipe can't help with, and for reasons I don't understand scaling down recipes, especially in baking, does not produce the same result. A recipe that starts with a 50 pound bag of flour is useless to you, and if you just try to divide all the weights by 100 the end result just isn't good. All you really know is that you can make good pizza dough with flour, water, oil, salt, sugar, and yeast. That is not exactly shocking news.

The issue with scaling in baking recipes is often that home bakers are measuring by volume and not mass. Any commercial baker is going to go by mass because with ingredients like flour the amount that's in 1 cup can vary wildly based on how firmly packed into the cup it is. There are also issues with how long you need to rest 10 pounds of dough vs 1 to ensure it properly hydrolyzes and the fact that pizza dough in pro pizza shops often undergoes a sort of accidental ferment just by nature of the fact that it's made in large batches then stored.
- That, but also certain things like yeast don't scale in normal ratios. You gotta use logs and powers and whatever them fancy math boys do.
- That is a problem, and also as someone else pointed out the yeast is another, but also in my experience water is as well. I don't know if it just dries out differently because of the change the in mass to surface area ratio or what, but for whatever reason you have to change the ratio of flour to water when you change the scale of a recipe. It can even make a difference just to be at a different altitude. Baking is a weirdly complex mix of chemistry and even sometimes biology. The more I learn about it, the more surprised I am that it ever even works.
- Are you aware of the metric system?
a company like Cisco

Networking AND food? What more could you want
- Yeah, I had a brainfart there. They're pronounced the same, but the company I was actually thinking of is spelled Sysco.
and a proper pizza oven. The oven a recipe can’t help with

Fortunately, it sounds like pizza steels do a really impressive job replicating a good oven.
- Yes and no. You can get amazing pizza just as good as a proper pizza oven with a pizza steel or a pizza stone if you know what you're doing and have a good oven, but again there are subtle differences that make it so you can't just replace one for a large pizza oven with no other adjustments and still get the exact same results.
- Tell me more about these pizza steels. I know of stone, but a quick google shows me that steels exist, but why steel over stone?
agree on scale, I've never managed to make a small batch of pizza dough taste right, but used to make restaurant batches 20 odd years ago no worries. I have no idea why it works that way

Nobody is really thinking about it, with all the other things there are to think about.

Also, restaurant-style recipes aren't that unique, any chef worth his salt should be able to come up with something similar. Unless its something really weird, and worth keeping as a trade secret.

Then you don't tell anyone though.

restaurant food is basically normal food with a metric fuckton of butter, sugar, and salt added

Plenty of restaurants source rarer ingredients than your local grocery store and use advanced techniques to create flavor and texture combinations that are hard and time-consuming to do as a home cook. It isn't simply "add more sugar, fat, and salt."

How much demand is there for recipes from shut down restaurants? Unless the restaurant had a food that was well known and very popular, the recipes wouldn't be something that most people would seek out anyway. Even the popular recipes may not be worth publishing as they may take special equipment or access to a supplier that the general public doesn't have.

Because they're busy going out of business, I'd imagine. It's actually a pretty complicated process if you want to avoid a bunch of extra problems down the line. If publishing the recipes helped avoid some of those problems, they might do it. But they're more likely trying to protect themselves from creditors and get their taxes sorted and final paychecks and selling inventory and equipment and real estate...

Maybe they're preserving the option to try again with a new restaurant?

Restaurant/chefs do sell menus to other restaurants/bars/chefs, so they may sell that off, but the public would never know about it.

Besides all the other reasons listed. The value of a restaurant is that they feed you with an unique experience. The recipe is not the experience, it's just a broad guideline. Everyone knows how burgers are made. But I've tasted some pretty unique burgers in my life, for which the experience of having eaten would not be possible to replicate even if you had a gram by gram breakdown of the constituent chemicals.

Food like burgers are also 85% technique and 10% equipment. I can't cook one at home the same I could back I the day in an industrial broiler.
- What is the remaining 5%?

I bet it's also common/planned that they would just reopen another one somewhere else. Esp if it closed for bankruptcy, etc.

Depending on the restaurant and the bankruptcy proceedings, the recipes may be considered an asset that can be sold to recoup losses. Those assets only have value when they are secret.