There are too many VBA-filled spreadsheets out there to allow Excel to disappear any time soon.
And I speak as somebody who regularly gets asked to update one such file for a client. This file has been around longer than I have, and I've been at my current employer more than 11 years now.
I've also seen a general resistance to learning anything new or changing working practices - especially in the larger accounting firms (I'm guessing they probably don't want the additional training costs in terms of both time & money for so many people unless it's really necessary). This means you can easily end up with a situation where people end up sticking with what they know & are familiar with using.
It may also be worth noting that whilst Libre Office supports macros it does so using its own language and not the same VBA that so many people are familiar with. A move to Libre Office would require a rewrite of those existing macros in files accountants are already using.