I got curious myself and agreed, so I went looking.
A lot of sources specified that it was part of a technical requirements checklist, and…
Yeap. It doesn’t explicitly require a “press any key” screen, but it gives a more pleasant screen to look at while you select a user. People online also say it’s used to detect which controller is in use.
If you add a feature like this to a game, it becomes harder to maintain if there are discrepancies between builds. So presumably it’s usually just left in rather than removed.