I don't get the "no" part: I think you're in perfect agreement with "irrational". There's heaps of COBOL that's very much staying. People are getting hired as junior COBOL developers in 2020.
"no" meaning no one is writing new programs/apps in COBOL, only maintaining old ones. "stay" meaning people will keep launching new programs/apps in PHP going forward.
I mean, COBOL is in the same boat -- there's too much code written in it to outright kill it. They still update the language standard today (2014).
The main migration argument I see is usually along the lines of "50% of all COBOL progammers today will be DEAD by 2025!"
Rather than about technical/financial merit (anyone willing to migrate on those grounds, and believed it was even possible for their infra, will have already done so)