Combine that with the needs of designers to "make the experience unique" to a level where consistency goes out of the window. Every commercial software these days has its own idea of design and it gets irritatingly hard to learn a new set of usage pattern for each.
Granted, the developer side of the story might happen as well but I'm guessing not that much (all the dev teams I've worked in saw an overloaded pipeline of work so it is very hard for me to imagine otherwise)
The number of designers who will march up to their VP and boldly declare that all the company's apps are just fine and don't need any kind of redesigning is small.
You get a similar thing any time a development team runs out of feature work or actual stress points in an application they maintain. They wind up reworking the thing mainly to have something to do to justify the continued paychecks until the business thinks of an actual reason.