Sometimes, a core job of IT is eating all the pain of using the old technology that the users already know so they can go do their job and the company can achieve its objectives.
The terminal apps, at least, have some history behind them and properly trained folks can be very fast with them.
But we're talking here about shitty early Swing-apps (or Oracle forms). If you've ever used one it can be incredibly frustrating. Moreover, people are usually just tossed into a role where they have to use these M-F-ing interfaces with no training. Who makes a table with cells too small to fit their content and where you can't resize the table? Oracle. That's who. And they're paid for it like you wouldn't believe!
To be fair, lots of software of those years were like this. SAP Ariba was just like this, and so were old Microsoft products
Encountered a similar issue many years ago at a company trying to sell a new ad booking system to Titan - they had crufty old VT100 based systems, the new one was fancy AJAX HTML whizzbangs. Exactly the same result - they could handle 5 bookings on the old system in the time it took to do one on the new (which was also terrible and ugly besides slow.)
Are you sure they wouldn't like a new interface if it was actually a real improvement?
I'm reminded of a story[0] about Norwegian doctors refusing to use the new GUI system and stubbornly continuing to use the obsolete text-based system. Were they luddites? No. The old system let them quickly navigate with the keyboard in seconds while talking to the patient. The new system required them to use the mouse, so they had to spend a lot of time focussing on using the GUI, rather than helping the patient.
[0] https://news.ycombinator.com/item?id=10289172