system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 What is the point of "press any button" screens on video games?
gpt
Usually, "press any button" screens happen after the game loads, or after your saved game loads, or after a new level loads.  (Or these days, after a long time of waiting for the game to connect to the servers.)  The game does not want to start/continue until you are ready though.  So, it has you input something to indicate you are ready.

Some games also use this as a way to make sure the controller works or the input is captured by the game (on Windows or other system that allows multiple things running at the same time).

Back in the days of arcade games, it would indicate for you to press the start button after inserting coins.  This would allow the demo screens/mode to run even if someone dropped a coin in and then walked away.  The start button would allow the intro to play, and then the player would start playing.  If you think about games like Pole Position, Pac-Man, or Donkey Kong, the delay for the start button ensures that the player is ready, and does not lose a life because they were not ready.  With two-player games, the start button would also indicate if one person simply put double the money in (with the intention of playing twice or being able to continue after losing the game) or if two people put money in for two-player mode.

Many things in video games have their roots in arcade games, and "press to start" is one that comes from that, even though the reason for it has changed some.

(On a side note, the "three lives" system that is occasionally still present in modern games is from arcade games.  The early games were simple, but the designers did not want a single death to end the game.  On the other hand, they wanted to limit how long a player could play before having to deposit more money.  This idea came from pinball, where a player would typically get three balls -- insert testicle-based joke here -- and three worked out right for the number of lives in arcade games in the late 1970s and 1980s to the extent that it became nearly universal.  Even when there were not coins, on the early consoles, the idea of three lives was so deeply ingrained that console games continued to have three lives per "play".  After you died three times, you would have to "press start to continue"!)