and to think some of mine get used daily and they are over 50 years old....
I buy flints even less often and store them under the felt in the lighter. If need be I can burn quite a few fuels in my Zippo including gas, diesel, kerosene, lantern fuel, lamp oil, booze...that Bic runs out and you are SOL.
Wow that sounds cool. Can I use different fuels in my Zippo? It's not an antique one or anything just a cheap silver but genuine Zippo bought at Walmart. I will definitely try diesel, and gasoline, as my camp stove uses gasoline and I have been at a campsite, tired and hungry only to find out I can't light my stove since my Bic lighter had leaked out overtime:grumpy: I had to eat my Beef Ravioli Cold

I will also try BBQ starter while I'm at it.
Anyway I EDC my Zippo almost everyday as well and it has served me many times where I otherwise would not have had a light. Many uses I have found are somewhat unique but you may find yourself in similar need someday.
Lighting Fireworks at rest area in UT, or WY. Beats using my trucks cigarette lighter:thumbup:
Defrosting/loosening fuel cap on Reefer Unit. This sounds incredibly stupid and unsafe. It's diesel fuel and ignites when compressed; it's not as flammable and unstable as Gasoline. Anyway when it's 10f below zero and the reefer cap is frozen on; my Zippo has come to my rescue. I wouldn't want to use a blow torch/lighter or a simple Bic on this job. The Zippo works great.
Defrosting door locks.
Defrosting trailer lock. Yeah these get stuck too.
Defrosting chain locks on tire chains. They have simple locks on them.
WD40 works for defrosting also but it tends to gum thinks up pretty bad after a while. Also it's just easier to reach in my pocket then to walk 50ft to my cab during a blizzard.
Carefully burning the ends off heavy nylon straps
Burning loose threads.
This one sounds creepy, but it's a makeshift candle for times when I get to take a bath while on the road such as at a hotel, or some truck stops have great baths. I find the flame soothing

A great hand warmer and it gets used for that often.
This next reason is taught by instructors and is commonly used. Defrosting Brakes. Yes these commonly freeze up from moisture in the brake lines and prevent you from going anywhere; or you drag your tires until they smoke and catch on fire. Using a Zippo to defrost brakes is not fun; but it works.
And of course offering to light someones smoke. It gets used for that almost weekly. In most states smoking in truck stop diners is legal and common. And the people in there are very friendly and open to a good conversation while enjoying a smoke.
Those are my reasons. I can always be found carrying on my person a Multitool, a Flashlight, a "tool" with a sharp blade on one end and a handle on the other

(A Pen, a Zippo, a very loud whistle, my cell phone along with my cell phone charger. I wear Jean cargo pants and it doesn't look at all tactical or bulky. It's not everyday I use everything that I carry, but I have them for when they are needed.