How exactly they are going to make him pay? He may have an upper hand if they harass him and he can file a police report.
Not really my problem. I pay for comprehensive insurance so that all my costs (and any third party medical or property costs) are covered. I don't have to chase anyone for anything. If and how the insurer chooses to pursue the at-fault party for costs is up to them. I would suggest in my case, they will absolutely do so as we're not talking small sums of money.
There are several avenues an insurer can go down. Firstly I'd suggest they will send the at-fault driver a letter of demand (which he will probably ignore). Following that they can send the debt to a debt collection agency or choose to take the driver to court to recover costs. If the insurer obtains a judgement from a court, then the debt is enforceable. I'm not sure what powers courts have to enforce debts in civil matters, but it probably ranges from a court ordered payment to property seizure and maybe even salary garnishes (I'm not 100% sure on that last one).
The other option is he declare bankruptcy, which in itself has long-standing and serious ramifications.
Basically, the way it works here in Australia is that CTP (Compulsory Third Party) insurance is part of the registration of a vehicle. It covers a third party's medical bills and you can't opt-out of it. It doesn't cover property damage or pay for things like hire cars etc...
Insurance for property is optional, but you're a lunatic if you don't at least get third party property insurance (that covers the other person if you have an at-fault crash, but not your own car). Even if you drive a worthless shit box, third party property insurance is one of those necessary things you need to avoid the situation I've described above.
If you have a good driving record and no history of at-fault claims, car insurance can actually be quite reasonably priced (for what it covers). As a 30-something year old with a good history, to insure my vehicle fully comprehensively costs me about AUD$900/year and a portion of that is tax deductible (as I use my car for work-related purposes).
My father always said to me from when I started driving "always have insurance, in-case you hit a Mercedes". And even when I owned a car worth no more than $1500, I still had insurance for that reason.