1. Zippo lighter fuel tends to evaporate. The spark maker and the sticks that it lights don't. I think it's a marketing tool more than anythng.

2. Very good point. Works for me. I carry several cheap small lighters in my gear. I test them every few months and replace those that don't work. Even if the gas is gone, they still throw sparks.

3. The main reason people carry fire pistons is they were dropped on their heads as infants. Hey, maybe some people like spending hours to get a fire going. Beats me.