Consider systems like the GDS infrastructure backing the travel industry. These systems are long-lived (50y+) and are the backbone of all travel booking and scheduling. The only thing that matters for them is not the end user experience, it's the stability of the system, and society's reliance upon its operation. It's robust and it was produced at the right time to carry an industry into the efficient monster it needed to be to succeed. A whole industry was built on it layer by layer, and what we now have is a complex beast composed of ancient IBM hardware, crazy nested and disparate schemas, greenscreen scrapers, and probably more than a few dashes of COBOL. One can't expect the system to stop evolving while we take a 5 year breather to rewrite it all.