Not uncommon for Australia. The housing market is very competitive so being a nuisance as a buyer, such as hiring someone for a thorough inspection, could hurt your chances.
What inspectors actually do also depends on who is engaging them and how much they get paid. For example, in the ACT it's mandatory for sellers to have an inspection done. This will generally go to the lowest bidder and they will put in minimum effort, e.g. the report will have things like "Roof inspected as far as can see from ladder placed against the house" and "furniture present, unable to inspect area". If you were the buyer and engaging an inspector, and the seller cooperated, you could have them inspect as much as you were willing to pay them for.