The attack you describe (somewhat dismissively) is extremely common.
For private phone contracts, we should kick the arses of our politicians and the regulatory agencies to finally do their job.
Only if you're willing to trust the reset process. The whole point of this is to remove that trust.
Further, as noted, this doesn't just protect against that attack. It also allows for filtering at the data layer, so you can remove malicious traffic. And it also gives SIM a stronger identity, so if you're using a heuristic for identification (as you always are) it becomes a much more powerful entry.