Scanners have gotten better recently, meaning they can tell the difference between water and explosives, but these restrictions weren’t pulled out of thin air like many others.
https://en.m.wikipedia.org/wiki/Security_repercussions_due_to_the_2006_transatlantic_aircraft_plot
There was a thwarted terrorist plot to use drink bottles to hold explosives.
What do you mean by “backed” here? I think I’m misunderstanding but I thought (and a short google seems to confirm) that currency A being backed by currency B means the value of A is fixed at a certain amount of currency B, and there is some organisation “backing” this with reserves.
Not trying to shill/defend crypto, just confused on terminology :)