I think their point is more that it's easier for an undocumented individiual to disappear than for a documented one. They're already undocumented, so they're used to operating without going through proper channels. They have no connection to the vehicle, and thus no insurance, and thus the person being hit has no recourse for getting their own vehicle fixed.
Now, letting them get licenses would presumably come with them also getting insurance, but I feel like this is just a band-aid on a much bigger problem.
Reminds me of that video where the owners dressed the dog like this and let it loose to chase after people at night.