As to why the customer had such a low limit policy, I can tell you that State Farm is the king of selling crap policies without recommending upping the limits. My company sends me things about this all the time, and as a result, I'm the most insured SOB on earth.
Hmm. How is this right enforced? Is is a statute (I think that's when a specific law is legislated, written down in kind of a rule book), or is it case law (I've been told this comes down through appeals), or tradition? You speak with confidence about "rights"--I don't understand what sort of right you mean.
Now, just as a citizen with only sense for my tool, it would seem very dangerous to force an insurance company to function the way you suggest we have a "right" to expect. If an insurance company cannot quarrel with a demand for payment, it will not be in business very long. I'd like to understand how this works?