That may be one part.
But another part is companies that need to demonstrate to their uses that a version change is a big change.
Microsoft is (im)famous for this: as far as I can tell, there has been little need for the constant UI churn in windows aside from convincing users that a new version is big enough to warrant that appellation (as opposed to a service pack/patch).
So I don't know where this conspiracy theory comes from, but it's entirely unfounded unless you're talking about a designer like Jony Ive with the power to go through multiple obstacles with ease, in which case the change isn't happening to prove he's needed but because he has a different vision.
Definitely not the case everywhere.
I had used excel 2003 until I was forced to use win 10 at which point it barely functioned anymore (i.e., it worked great in win 7)
I still miss excel 2003, it has been downhill from there
As for accounting software, they all mostly stink though serve a purpose in larger companies where you need some degree of separation of duties to reduce (at least in appearance as much internal control is theatre) error/theft risk...
In all fairness, back them I also had to use MS Office for certain other tasks, but luckily I don't need that anymore.
Now there is Confluence instead however to mangle our docs and waste our time.
And I don't hate the ribbon interface, I think it's totally fine--but also, in Excel specifically, I almost never click a button on it.
QuickBooks's online version, on the other hand, has terrible discoverability and doesn't have standard keyboard controls.
The Excel data format has changed once, significantly, in the past 2 decades (which was forced on MS and even though MS has tried to sabotage the openness of the new formats they were required to create, its still much better than the predecessors).
It’s hard to think of any other change that wasn’t just an addition (new formulas, higher column/row limits).
But, importantly, that data format change didn't mean you were forced to stop using the old format.
Excel UI interface changes but it won't change your spreadsheet content, which is the core functionality Excel users care about.
I've been using 15 year old .xlsx files with no issues across Excel 2007, to 2021, and Excel online.
I've seen companies using files with an absurd amount of worksheets within the file, or with an absurd number of rows (up to the limit), and those haven't been broken.
And I don't remember transitioning from xls to xlsx to be that painful, but this might be untrue for people using some very specific features.
The problem with all of these enterprise web applications is that they all suck. I worked for a big government agency that transitioned from a mostly homegrown, mainframe 3270 based accounting system to PeopleSoft. The staff revolted.
We joked about the “Revenge of the Beancounters”, but looking at it, they were right. It took them 4-6 months to train a new person with the old system, but they were hyper-productive. With the new system, they actually needed to grow the staff because you couldn’t build out workflows that the business needed.
They did get some benefits, like improved payments and invoice tracking. (Which drove the business case) But the general financial operations suffered.
Are your accounting people quite young? Excel moves and changes stuff, though not on quite such an aggressive timeline. Modern Office is not like 1990s Office where you buy it and then it doesn't change unless you decide to change it.
This is fine, the universe's one constant is change, if we fight it we'll lose, but it's worth calling out that there will be change, just some of these outfits are taking the piss.