Remember this is throttle body injection, not true 'fuel injection', it's a set of injectors mounted inside the throttle body. It's a halfway point between carbs and fuel injection (what cars in the 80's had).
And, like those cars in the 80's, start up isn't as easy and smooth as TRUE fuel injection, so while those other reasons are true (fluid warmup, voltage, etc.), it's also needed to help it start smoother and not stall. Think of it like an automatic half-choke, because, essentially, that's what it is. The throttle remains in the same position, but it runs extra rich at start up.
Also, there is some virtue in letting any vehicle you have warm up for a minute before you take off. Not up to operating temperature or anything, but maybe hit the starter button before you fiddle with your helmet and gloves or whatever, give it a good 30-60 seconds. The reason is, that will get the oil pressure up, get oil circulated to the top, etc. Your engine can be 'starved' of oil in it's first few seconds of running, and if you immediately go from start up to a couple thousand RPMs + a load, it can, over time, wear out faster than if you had warmed it up. I don't think you're going to blow the engine up instantly doing it, but it's probably going to last you longer if you just give it a few seconds before start up.
Edit: Stickied, thanks to that great info on the idle set screw.
If anyone would like to do a write up on that, maybe tear down their own TB and take pics, let me know and send me a PM, and I'll replace this thread with whatever you write up (giving credit, of course, where credit is due to Mister Orangepeel for the discovery)