Please someone tell me why it take years to develop a game

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I haven't really created a game so I am not initially sure why it takes here but here are the reasons I believe it is Money as the creators need money and other developers to help him/her developing the game. Discussion when it comes to gaming or anything requires Planning I believe like what the creator wants to see in game then comes Polishing the game and adding trailers when E3 comes around and yea that's it reallyy