Why does ballistic ammo have range in space? Shouldn't it travel at the same speed onward until it eventually hits something?

So there's multiple things there. First of all, I would draw the game card. If we had unlimited ballistic ammo ranges, you could sit 20 kilometers away from a Hammerhead and just kill it right there, given enough time. That's not fun. And there's not a lot you can do to counter that. The second thing is, if it just keeps traveling forever, you get into a situation where you need to track all these bullets on the client and the server. And given how high our fire rates are sometimes, it just wouldn't be maintainable. It would be very expensive. I mean, this is again the real-world question. Also in the real world, there's a lot of ammunition that has an integrated timer. So it blows up after having flown for three or four seconds just to not have some bullets hitting a poor guy on the street somewhere else. So I think it is okay just to go for the gamey part here.

I imagine the physics system, if it had to track every bullet that was ever fired infinitely across the entire system, that would cause some unnecessary...

That's primarily why we had a lifetime, back in Arena Commander 1. You can blame me.