Why not issue all the Bitcoins at once What is the point of mining the Bitcoin and thus issuing new Bitcoins over the span of some time versus simply issuing all 21 million coins at once?
In a way, all bitcoins were issued with the genesis block: The total number was fixed and the distribution schedule defined with the rules put in place then. However, distributing them over a longer period of time allows for the bitcoins to be spread out more, creates incentives for miners to contribute work to the Bitcoin network and probably also helped fewer of them getting lost during the emergence of Bitcoin when many people just tried it briefly and likely didn't properly store their coins.