When I have travelled elsewhere in the country, they just seemed to grab 4 to 6 people as they are passing through security. I can not offer any point of view regards elsewhere in the world, but at least here, it seems to be related to how much random disruption they can cause to all types of travellers.
I know that our government is getting more and more "afraid" of any kind of "terrorist" that they are willing to bring in more and more annoyances and intrusions. I have also seen some of the security inspection staff being more apologetic for increased intrusions.
It's just a fact of life that fear is being fed so that a greater control over the citizens can be created. This is irrespective of political affiliation any of our elected politicians may have. There are many people that I have discussed this matter with and they express the opinion that such policies should be in place because "fear".
As citizens, we need to start recognising that we are the ones who can elect people who will stand strong against fear and will do something to bring about an increase in the backbone of society. However, the citizenry of Australia seems to be focussed on many matters that don't matter.