A software had been developed over a decade ago. With critical design problems, it grew slower and buggier over time.
As a simple change in any area could create new bugs in other parts, gradually the developers team decided not to change the software any more, instead for fixing bugs or adding features, every time a new software should be developed which monitors the main software, and tries to change its output from outside! For example, look into the outputs and inputs, and whenever there's this number in the output considering this sequence of inputs, change the output to this instead.
As all the patchwork is done from outside, auxiliary software are very huge. They have to have parts to save and monitor inputs and outputs and algorithms to communicate with the main software and its clients.
As this architecture becomes more and more complex, company negotiates with users to convince them to change their habits a bit. Like instead of receiving an email with latest notifications, download a csv every day from a url which gives them their notifications! Because it is then easier for developers to build.
As the project grows, company hires more and more developers to work on this gigantic project. Suddenly, some day, there comes a young talented developer who realizes if the company develops the software from scratch, it could become 100 times smaller as there will be no patchwork, no monitoring of the outputs and inputs and no reverse engineering to figure out why the system behaves like this to change its behavior and finally, no arrangement with users to download weird csv files as there will be a fresh new code base using latest design patterns and a modern UI.
Managers but, are unaware of technical jargon and have no time to listen to a curious kid! They look into the list of payrolls and say, replacing something we spent millions of man hours to build, is IMPOSSIBLE! Get back to your work or find another job!
Most people decide to remain silence and therefore the madness continues with no resistance. That's why when you buy a ticket from a public transport system you see long delays and various unexpected behavior. That's why when you are waiting to receive an SMS from your bank you might end up requesting a letter by post instead!
Yet there are some rebel developers who stand and fight! They finally get expelled from the famous powerful system down to the streets. They are free to open their startups and develop their dream system. They do. But government (as the only client most of the time), would look into the budget spending and says: How can we replace an annually billion dollar project without a toy built by a bunch of kids? And the madness continues.... Boeings crash, space programs stagnate and banks take forever to process risks and react. This is our world.