They’re not rich ghosts who can shrug off the loss of a vehicle and disappear. Most are, in fact, tethered to a small area BECAUSE they’re undocumented, and as such can’t rent or buy housing or cars anywhere, and the vast majority are in jobs that are, at best, scratching the floor of the middle class.
This argument makes it even more appealing to get them licenses and therefore insurance by tying the car involved to a name.