If managers are so good at managing things, how come they can't manage to manage themselves?

Middle manager in an IT company here. My job description is saying "no" to requests outside the official pipeline, in order to shield my team from outside interference and burnout. I need a manager to fight for me whenever I pick a fight with one of the VPs who think we need to drop everything and refocus on their pet project.

manager here. I'm just a jerry. I kept crawling, and it kept working. I don't like it any more than you.
- I made it to jnr management by being too stubborn to resign under any of the previous ones.

It is not easy to manage oneself, but easier to manage others. Like a mother can get her children to brush their teeth and reminde them to do so, but she may not brush her own teeth. Very good manager are however very organized and efficient. They do manage themselves.

When you have too many people working somewhere, it becomes impossible for one person to oversee everything. So you get multiple managers managing more specific groups, and then managers who manage the entire segment without knowing all the details or people. When a company gets even larger you'll need even more layers. There's only so much time and mental capacity that humans have, so at some point you need some multi-threading by involving multiple people.
To me it kinda makes sense, and I don't really know how I'd do it differently if given the chance, but the higher level management does always seem to feel like some people making decisions high up in their ivory tower without knowing what is actually going on.

Kelly- I manage my department, and I been doing it for several years now...
Jim- Your department is just you right?
Kelly- Yes Jim, but I'm not easy to manage...

For a real answer:
A manager can control what is done under them, but if one of their teams/members needs something done by another team they have no control.
Their manager might control the manager of the other team though, so the decision goes up the line until it hits someone who has both sides of a problem under them and can make the decisions on priorities/cost etc of the requested action.
In small companies, this may just be one or two layers, but in bigger companies it becomes a disfunctional disaster.

It seems that managers managing the managers cannot manage to manage the management of managers and therefore we need managers to manage the management of managers managing the management of managers.
- Buffalo buffalo buffalo buffalo buffalo.
- It's a hierarchy. You have a department, or other such division, with a manager to coordinate it. Then you have a manager who manages all the departments, or a subsection thereof, to coordinate them; this is "managing managers" and typically more complex due to the interdisciplinary nature. Then you have managers to manage the manager-managers, who oversee entire regions or similar sectors.
  Sometimes manager-manager managers are necessary, but if you need managers to micromanage manager-managers, your organization has problems

It sounds like you have an example to share.
- Luckily I've been self-managing with a rather free-form management style for the last few years! But I have now updated the original post to clarify my point.

I love me a good manager. Luckily I was able to work with a few in my lifetime. The good ones have no problems managing your and their own work.

Myself and some other managers I know became managers for being competent at our science-based jobs when the company wanted to expand. Our education and career up until this point mostly had not involved learning skills like delegation, teaching, scheduling, and team-budgeting, not to mention the interactive social skills needed to successfully manage individuals.
Some bad managers are just good workers that weren't able to suddenly learn these skills when their employer insisted they manage a team so it could pursue its endless quest for infinite growth by setting up hierarchies of workers. Good managers are either trained in management or extraordinarily talented.

Ah, same as a real mathematician can mathematically mathematise mathematics in a mathematical mathematiculation, so if a mathematician can mathematise mathematics in a mathematical mathematiculation, why can't you mathematically mathematise mathematics in a mathematical mathematiculation like the mathematician who mathematically mathematises mathematics in a mathematical mathematiculation..
- I like this answer best.

When I was in warehousing, it seemed like it was the people to kissed the most ass that ended up in management, not the people that were capable. The quietly competent workers stayed in entry level positions, some of them for decades. And over time, more and more of these positions are created till you have guys that do nothing except drive to different warehouses for 'inspections'. We'd have 3 or 4 different managers come through multiple times a year, rent a convertible to drive across the country, stay in hotels, have all meals paid, to walk into a warehouse for 15 minutes and then leave. Sometimes one would come just weeks after another. We always had to work extra hard to make sure the warehouse is spotless, and they often wouldn't even walk around.
Meanwhile, we might get a pizza once or twice a year, and wages were capped. Ask for a raise? Can't afford it sadly
- if you need the manager to come to make sure the warehouse is spotless, do you even do your work when the manager not around 🤷🏻‍♂️
  
  You've never worked somewhere when "higher ups" are coming? Supervisors start freaking out and obsessing over the smallest details, and most of the time the people coming either never set foot in the building or they have no clue what they're looking at in the first place.

This is because managing is the easy part of the job. You have to have someone to push and threaten you to do MORE and MORE for the same or less pay, then dangle that carrot in front of you and keep moving goalposts.
source: was a top manager in the country of a certain tire chain.