Most of the time, companies can use newer technologies to replace or fix this bad code, but if the spaghetti code is still needed or in use, then it becomes too difficult or expensive to fix. So we end up with old, badly written and inefficient code and are stuck with it indefinitely.

Good example here being Windows. Some programs from over 20 years ago will still run on Windows 11, many companies rely on these older programs and Microsoft knows this. However, the systems written to allow these programs to run in Windows is usually seen as being bad code since it lacks a lot of the modern techniques programmers use to make things easier to work with and maintain over time. But these old systems cannot be changed or updated since they will then not work with those 20 year old programs that many companies rely on.