'Hairdresser' is also considered to be in short supply. Here's a list of all occupations (in case you didn't know): https://www.nwivisas.com/nwi-blog/australia/australian-skill... . This list had a bunch of occupations removed earlier this year; bad news for everybody looking to emigrate to Oz to take up a lucrative career in picture framing, because "Picture Framer" is no longer eligible for a 457 visa.

I realize that your actual remark is to the 'why' of some professions being on this list, I'm just pointing the above out for non-Australians like myself who might be amused by these things when seeing them for the first time, like I was.