That's fine if you're building something that's already been made. Games don't do that, when you push the boundaries you need to know how your math works. You won't get more performance than the competition without understanding the tools you are using.
It didn't need it. That was just the solution the devs created. They could have done it with 32-bit floats, or hell, 32-bit integers, if they wanted, given the right representation. But they chose 64-bit floats to solve the problem, the problem did not choose 64-bit floats.
It really does need it. 32 bit positioning breaks down fairly quickly on planet scale. Shifting the world origin is not a streamlined process and doing it frequently for each client in a large multiplayer game is nearly prohibitive. You could invest the effort into making world shifting and planet scale work in 32 bit, and the lesser of the two evils would still be implementing 64bit positioning. You gain so much and lose so little for having done it.
