I actually worked on Office performance many years ago. We did a lot of very clever stuff to improve the product, even to the point of optimizing the byte ordering on disk (spinning rust) so that the initial boot would be faster.
That said, it always felt a bit like a losing battle. The goal was "make Office not get slower". It's very hard to convince app teams that their new shiny abstraction or graphics object is actually the reason everything is worse, and it's even more challenging when there's no direct impact- just a broad increase in system memory pressure.
Typically, perf isn't a few bad decisions. It's a very large number of independently reasonable decisions that add up to a bad result. If the team loses that discipline for even one moment then it's very very difficult to fix. I wonder if my former team still exists or if they've all been reassigned elsewhere.
Some car dealers have installed private car washes. Come in for a free wash, any time, as long as you own the car and are displaying the dealer plate. So at least in that case they're "paying" for the advertising.