Lots of people used to do their own bond cleans, some still do. I've had one done recently, and it was almost half of the actual bond when carpet cleaning and gardening was added.
When did it become this thing that houses should be in showroom condition (as against just clean)? Has it happened in the last 10 years?
When agents started realising they could profit on bond claims. Where I live, if you give up their very brief time frane/opportunity to fulfil all requirements, they can take as much as they like from the bond. Safe bet for them is that most renters need some of the money back soon rather than none of it if it goes through arbitration.