Science of course! Maybe you simulating the entire universe for science is a thing you want to do, but there's no reason to think you'd want to (or even be able

Science of course! Maybe you simulating the entire universe for science is a thing you want to do, but there's no reason to think you'd want to (or even be able to without simulating the earlier bits) t=4.5 billion years rather than t=0. And the numbers I gave only allow you to simulate roughly in realtime, so... your civilization has to stick around for another 4.5 billion years to get to us.