This is due to the way how incentives are aligned. Systems that are powering things for, say a decade at least but worked on Quarterly basis.
Why is this alive and well, then? Because it doesn't actually matter as long as money keeps rolling in. It is also possible that the losses caused by or efficiency not achieved do not show up in the accounts.
This really is the worst, and that's why I left my first job. Funnily enough, I just took that job back after a few years but I am now the lead and sole developer on it, I'm having the time of my life doing what I've always wanted to do back then, and seeing the product now flourish.
The bad code didn't really matter, it was the fact that I was not allowed to improve it and forced to build new features on top of crappy code that made me quit in the first place.