Curious as I was pondering why….does appear to have been at least one available, if they were being truthful: https://www.bladehq.com/item—Titaner-Titanium-Zippo-Lighter-Case—87594
My thoughts were about the manufacturing process to create a thin shell. Grade 2 is the most common in consumer goods and it’s reasonably ductile but to be able to form such a small item as a lighter shell it would have to be awfully thin stock with $$$ dies that require more frequent touch-ups or replacement ($5000.00 would be on the low end for such a die and they can easily be 4-5 times higher in cost for more complex dies). They would likely have a higher failure rate from stress cracks and such, further increasing costs. Larger goods like the popular backpacking pots/mugs are easier to cope with (I think there are still only three main factories that produce those, plus whoever SnowPeak uses, and they’re all drop forged). Grade 5 is the strongest commercially available alloy but it’s generally machined or roughly forged and finished from solid stock, rather than formed. “Pure” titanium is out there and maybe could be used for this since it’s softer still than Grade 2, but oddly it also costs more (or used to). Additional cutting or machining features, or welding, add further even though that’s fairly common work for good machine shops these days and less expensive than it used to be. Maybe for the relatively small market of Zippo shells it’s just not worth the effort/investment.
Comparing metals…it’s density. If you were to compare like thicknesses between “any steel” and “any titanium”, Ti will come out on top with most metrics but you know it just depends what you’re after and these days there are some Really Freakin’ Impressive steels available if you want to pay for them. The beauty is that you can get similar “strength” in a titanium product using far less material and thus much less weight. Any metal can bend and flex when thinner…heck you can even buy very nice titanium foils (thicker stuff, not jewelry type foil) that has a lot of great uses and qualities, and it can be held together with typical office staples. But even when thin, titanium retains a lot of advantages over steel. In aircraft, correct me if I’m wrong, but the use of titanium had more to do with heat stresses and dimensional stability at supersonic speeds rather than weight. It had a host of challenges that had to be worked out but it was worth it despite all of that, for the application.