I wonder if there are any places where the law requires that such structures be insured?
It would make sense to insure them, since the cost of removing the debris, cleaning up the site, and building a new KH would be substantial. Didn't they request that congregations should send everything to the HQ aside from whatever was needed for one or two month's expenses? If they still do that, then no congregation would have the means to even clean up the site, much less rebuild.
And the WTS would probably get a bargain-basement rate, since they could insure thousands of properties instead of just one. I don't think they could use this to skim money by using cheap labor, since that would be fraud in at least a few countries. But I don't know if the potential cost-savings of not insuring them is worth it.