Airline crew here. Welcome to my world!
Every single working day of my working life (I’ve been flying since before 9/11) has seen me plagued by random, ever-changing security rules which are completely different from airport to airport, sometimes even different between security channels in the same airport. And there is no rhyme or reason to it. You just have to guess what the rules are today. I’ve had the pleasure of flying into and out of 123 different airports during my career, and played ‘what are we allowed today?’ at all of them. Because sometimes even what you were allowed yesterday isn’t allowed today. And you can’t argue with it. Or them.
Sometimes liquids are fine, they have the scanners.
Sometimes not.
Sometimes they have the scanners but they are overly sensitive.
Sometimes electronics have to come out of the bag.
Sometimes electronics are only allowed if their battery isn’t flat.
Sometimes Kindles are ok but laptops must come out.
Sometimes Kindles are fine.
Sometimes your shoes must come off.
Sometimes your shoes are fine.
I’ve had a bottle opener confiscated because of the deadly corkscrew on it, and a tiny Swiss Army knife (with a legal sized blade) that was on my keyring for over a decade but suddenly Not Allowed at one airport. In India you can’t even bring nail clippers or powdered spices. Cinnamon bark ok, cinnamon powder absolutely not! I’ve temporarily grounded a flight while I argued with a security officer about a sewing needle (‘sharp points not allowed? What about our name badges?’) and another time about the size of a spoon.
All of it is intended to improve the safety of aviation, but it is so arbitrary and many of the rules moving goalposts that it generally serves to frustrate. And the equipment is still not perfect, and certainly the job of airport security officer is not well paid and is a thankless task. Remember- if it all kicks off and an aircraft is brought down by a terrorist or lunatic, the officer who allowed the offending articles through will be scrutinised till they wish they’d never taken the damned job to begin with.
You’ll never change things, and they are not likely to improve. So just nod, smile, remove your belt, and don’t assume anything.
If you really need something, such as prescription medicine, take it in your hand luggage with a copy of the prescription and try to bring a new unopened packet as they are often viewed as ‘safer.’ They cannot confiscate prescription medicines or milk for babies, but they can examine it and test it - after all, a terrorist will disguise the tools of their trade in any way they think they can get something through, without morals or scruples. They have used the belongings of family members including children and partners in the past to try and sneak things on they could bring down an airliner with.
If you don’t really need something in the cabin with you, you just want it (your perfume, your week’s worth of toiletries because you are dodging the baggage fee/the wait at the carousel etc) then just put up with it. You can avoid increasing your exposure to the vagaries of the security search by taking less through it. You can always put it in the hold.
There are new threats and risks appearing all the time - eg we never used to have to worry about lithium battery thermal runaway but now it seems it’s not a proper day at work unless someone has dropped their phone, AirPods or even entire bloody laptop down the side of their moving seat and now risk accidentally crushing it with potential subsequent fire if they return to the landing/take off position. So things will continue to change.