I think the biggest issue with the 457 program, is the ease of access.
Whilst it isn't that easy, when compared to some other countries it is a walk in the park.
Gaining work visa's in other countries can be quite difficult.
Under the 457 you can apply simply under your qualification, nominate your sponsored employer and you are away.
In some countries, you need your qualification, your employers sponsorship and the reason you should be given permission....i.e 10k hours as check and training captain.
Case by case rather than carte blanche by job title.