Of course cost is also a major aspect. Random article claims that "Until recently, it [IBM] was spending over a million dollars each year to license Neue Helvetica for the company". With that sort of money you can afford to make your own fonts too.
While I'd agree that e.g. the Netflix font was somewhat non-remarkable/forgettable, I think they did manage to capture surprising amount of IBMness into Plex. I noticed it on their docs pages before they made big fuss about it, and really remarked to myself on how neat the font was.
Plus, if their push is to tie the font back to IBM strongly, allowing anyone to freely use the font is good press, so why not?
Apple's always had their own typeface, though I don't remember them using one as heavily as San Francisco. But it feels very in-character for them.
Samsung did it, I suspect, because Apple did.
The key difference being that Garamond is a classic on its own, and Myriad is even the default font in Adobe products (at least InDesign).
That's exactly what I was getting at, thanks!
What are some other corporate fonts?
If I ever see this font again, I probably won't even know I'm looking at it.