Airports

Why do the rules for baggage control differ so much between airports or even flights? One moment I'm breezing through security, and the next, I am asked to do a striptease.

Case in point: from Australia's Sunshine Coast to Sydney required me to remove all liquids, take out my laptop from the bag, take my belt off. Good thing I worn flip flops. All for a domestic flight!

However, when it came time for my international flight from Sydney to Dubai, I only had to empty my water bottle, laptop in the bag. And once I was in Dubai, full bottle of water in my hand, it was a smooth sailing experience: "All good, mate. Just walk through." But had my passport checked 3 times before I boarded!
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Anyone knows?