Disposable lighters work really crappily in very cold weather. Flint and steel and the friction methods have no issues with cold; the Inuit relied on the bowdrill. Even on tropical islands, there are other “mentalities” to starting fires than “What’s the cheapest and easiest way to make fire?”. Flint and steel was used for more than 1 000 years as the main firelighting method. Many people want to be part of that continuity. Friction fire methods go back at least tens of thousands of years, covering the entire Homo sapiens story, possibly much farther back (use of fire extends easily into the Hominid era, but it is not known when active firemaking was adopted). It is really a rush to make friction fire in the woods, even after a couple of hundred successes. Making a fire with a lighter is a resounding meh in comparison. As no-one today heads into the wild because they have to, these things matter. (Stroud and any other savvy survivalist carries boring firelighting gear as backup, anyway).
Or an empty can could be made into a alcohol burning soda can stove, two real uses in one!
CMC fnord!
I carry two disposable lighters and a mag bar on backpacking trips. The mag bar is my won’t fail backup. I always carry a pill bottle with 100% cotton balls soaked in Vaseline for tinder. They work well with the lighter or mag bar.
this is cued up where he scrapes the bar and ignites the shavings.
mag bars aren’t created equal. Some are made poorly and junk. Always test your gear before you go backpacking or camping.
Even with a good polish, a standard sized soda can doesn’t give you a very large reflective area. A perfect excuse to bring a 25oz lager can instead. 
I carry a magnesium bar like this Coleman one. The little saw blade is glued to the side of the bar and a rod of flint is glued in the slot on the side.
http://www.coleman.com/product/magnesium-fire-starter/2000003266#.VKma0JU5CUk
I keep it in the top of a water resistant container. The bottom of the container is filled with strike any where wood matches packed in paraffin wax. The wax will work as excellent starter fuel. The container has a lanyard and a clip to attach to your outfit.
I hunt and fish alone, often out of cell phone range in the damp Pacific NW, and if I get lost or have an accident I will be able to start a fire.
The trick with the parabolic bottom of a soda can involves sunlight. Might work if you have enough time to work on the can, and enough sunlight. If you are lost in the winter on a cloudy day and you are wet, cold and possibly injured you are going to die before the can starts a fire.
Are we talking about survival skills and equipment or are we talking about primitive camping? What gives me a rush will take hind tit to what works quickly and reliably when I am wet, cold, and maybe injured or lost. I can carry three or four modern firemaking methods in three or four different places on my person without noticing the weight. In a genuine emergency, if I am fucking about gathering stuff to make a bow drill, then I planned and prepared very poorly.
I can’t imagine trying to make a complete fire bow on the fly, just from what wood can be found in the immediate area.