I think you may be getting confused between Home Warranty Insurance (which only applies to new buildings three storeys high or less) and mandatory building insurance which applies to all strata buildings and is there, among other things, to replace the building if it falls down.
In your case, if the building is more than seven years old, HWI wouldn't apply in any case, and I suspect the fact that it's four storeys would rule it out too.
But your building has to be insured for it's replacement value, under the Strata Act. It's not that expensive and the bigger the building, the more owners to share the cost of the insurance.