Liquid explosives are probably a bit more harmful than the <= 75% alcohol you can buy at the duty free. Not saying that the rules make sense, but that seems to

Liquid explosives are probably a bit more harmful than the <= 75% alcohol you can buy at the duty free. Not saying that the rules make sense, but that seems to be the reasoning behind them. Dealing with a bit of fire is easier than a hole in the fuselage.