Duty free alcohol cannot even sustain a fire, let alone "start" one. It isn't strong enough. Alcohol is NOT flammable unless it is 100deg proof or over, that being more or less the definition of "proof". Duty free/airport sales is never over 75-80%.
Surely you don't think the industry would allow, let alone promote the sale and carriage of flammable liquids in the cabin?
"liquids leaking into the electrics..."??? Oh purleeese!
I think you'll find aircraft designers considered that possibility a long, long time ago and designed it out...(about the same time it was realised that aircraft might occasionally be exposed to rain)
As to why a duty free bottles not allowed in the overhead locker in case they fall on someone - I've never heard such tosh. What about the cases in the locker that weigh twenty times as much? Aren't they a 20 X greater hazard?
What airline bans this? I've never heard of it!
If we're going to ask people to conform to rules it behoves us to ensure they're sensible ones and based in fact and reality, or we run the risk of discrediting them before we've even started.
Even so, pax need to understand that CC are there for three reasons, and three reasons only. they are;
Safety
Safety,
and Safety.
(And bringing the pilots their tea, which is the same thing.)
Any other function carried out when not engaged in Safety is purely an ancilliary job, and is entirely optional at the Captain's, or the Purser's discretion.
Put up with it, and behave like an adult when asked to do something by your Safety Professionals.