Microsoft and a lot of other developers used to add "credits" or easter eggs to their programs. At least for Microsoft it was the customers that complained about them. In retrospect they likely went too far incorporating full fledged games complete with DOOM style 3D engines [1], but it was a good morale booster for the developers and a chance to add some culture to their work. [1] https://www.youtube.com/watch?v=nwg…
As far as I know, they've since banned such easter eggs because of compliance rules (US federal laws require that all features of a product must be documented for a product to be considered for government use)
Except for those the US government requires, right?