You clearly have no idea of the economics involved.
I regularly deal with customers who have small-to-medium COBOL installations (relative to average sizes in the industry). That's a few hundred to a couple thousand individual COBOL programs, generally a mix of interactive (CICS and/or IMS) and batch (JCL) processing, with all the associated resources: flat files, databases, JCL scripts, screen definitions, system resource definitions, ...
Migrating to a compatible COBOL dialect and emulated mainframe environment on Windows or UNIX usually takes a year or more for an application suite like that. And that's with no source code changes. The customer has to figure out what they have in the application portfolio and its resources, build a test suite, get the gear in place and figure out how to administer it, decide how they're going to develop in parallel until the switchover happens (because development doesn't stop on the old code just because you're trying to move to a new platform), assign resources, figure out the environmental differences, take care of compliance and other legal issues, migrate, test, plan the switchover...
Migrating to a different language is orders of magnitude more expensive, in time and money. Yes, periodically organizations decide to junk all their COBOL and replace it with whatever turns the CIO on - Java used to be the popular choice, and often still is, though other languages are making inroads. We see a lot of those projects fail, when they're years behind schedule and have run over budget by several times the initial estimate.
Even our customers often do phased migrations, where they tackle one application at a time. That has complications of its own - because generally the migrated apps still need to interact with the ones still on the mainframe, so you have additional communications, data-access, and distributed-processing complexity to deal with - but it's simply not economically feasible for those organizations to do the whole migration all at once. And that's despite the fact that they reliably see savings for each application that they migrate, starting as soon as they can reduce their mainframe capacity, thanks to mainframe leasing terms. They know the investment pays off; but they only have so much to invest in it at any given point.
Saying that organizations should simply rewrite all of their COBOL applications is like recommending everyone immediately switch to plug-in electric cars. It's the same sort of pie-in-the-sky thinking.
 As noted above, I work for Micro Focus; not on COBOL, but on tech that's used by many of our COBOL customers.