I'll tell a story from my drinking daze.
I always believed in light weight, so on canoe trips I only took hard liquor: Scoresby scotch. I decided that even the glass bottle was too heavy, so I carried the Scotch in a one liter aluminum Sigg fuel bottle. These were used for Coleman fuel and were red and sort of torpedo or bomb shaped.
In my business life I was flying a lot for several years. Being too cheap to spend my money in hotel bars when traveling, I began to bring my own bottle in my carry-on suitcase. Since my lightweight scotch philosophy had served me well on canoe trips, I figured I'd save some suitcase weight by using the same Sigg fuel bottle trick. Smart guy, I was.
Then, sometime after the Iran hostage crisis and the airline skyjackings in the 80's, airports began X-raying carry-on luggage!!!
"Code 83, Code 83, BOMB ALERT, BOMB ALERT."
As I sat there talking to the FBI or Secret Service or whoever the heck they were, I sensed there might be a problem.