These are actually some arguments against continuing to support it:
1) Some background--I work at a lawfirm where the owner insists on using a hobbyist DIY DOS database manager that was never popular, to write a database system even though she's not a programmer. Symantec abandoned the database manager in 1995, and we use an earlier version developed 1986-1991. The database manager has a proprietary file format, doesn't allow multiple tables or screen sets, has no query language, no programming language, no IDE, cannot read or write any data format other than plain ASCII, does not have strong data typing, and on and on and on. And she's not gonna get anything modern even though since mid-2014 she's been told by me and every consultant that she needs a modern Windows-based program written by a developer.
I'm 69, a lawyer with no formal I.T. training. I've told her straight out "Whenever I leave, you won't be able to find any competent I.T. person. No one under 55 knows anything about DOS--and they won't be interested in learning. Plus, any I.T. person will know that working with this stuff 2-3 years would be career suicide. "At your current job, do you work with C? No. C++? No. Java? No. SQL? No. Python? No. ..." They couldn't even list DOS on a resumé."
2) Related to that (and relevant to this topic), I've told her, "Microsoft is fully integrating Linux into Windows--but only in 64-bit Windows. They're doing it to get access to billions of lines of Linux code and hundreds of thousands of routines. Within 2 years, ... maybe 3 at most ... some client (major hospital systems) is going to tell us they've upgraded their system and we need to use a different on-line interface program--that only runs on 64-bit Windows.
"Plus, most major software vendors are no longer supporting 32-bit or already plan to phase it out. Once WSL is an integral part of Windows, within 2 major versions the software companies' developers will start using that--they won't bother writing separate equivalent routines for 32-bit versions."
3) Yes, there are "mission critical" applications that only run under 32-bit and no longer have vendor support and there is no equivalent replacement. But does that mean that a relatively small company with a narrow specialized customer base should continue manufacturing 5-1/4" floppy disk drives? Or 19" CRT monitors? Or VCR's? Or 1MB RAM sticks?
(For "You young-uns" that's one MEGABYTE sticks, not one GIGABYTE. ... Ask your grandpa ...)
And does that mean the company should continue developing and manufacturing for the customers who could get something equivalent but just "continue to hang on"?
4) Realistically, at some point Microsoft is going to stop developing and supporting 32-bit Windows. They have already publicly indicated they want to move to "Windows As A Service". Can you really see Windows 10 ver 2410 still having a 32-bit version--that can't tie in to WSL? And that's just 5 years down the line.