> "why would I use Bitcoin when I can use existing payment methods?"
Bitcoin can be used for other reasons beyond payment system transactions; for example, a bunch of coins are stored in cold wallets, as a physical store of value which cannot be confiscated. Market fluctuations still happen but that's unrelated to physical coin storage.
I've never believed this line of logic at all. You really think in a serious shit-hits-the-fan scenario (be it natural disaster, government takeover, whatever) you are going to have reliable internet connectivity?
During relatively low intensity conflicts mobile networks usually work, e.g. in Syria or Ukraine. I think it's the most common scenario in the modern time for shit-hits-the-fan.
Yeah, I expect sneakernet to work pretty well. A few weeks is way better than nothing. Also, you don't need to use an active internet connection to make reliable zero-confirmation transactions (see lightning network, although it's true that monitoring for confirmations requires internet data- so you have to set the timeouts to be way way into the future, which is reasonable and not unexpected).
Yep. Double-spending zero-conf transactions can work as long as you are using a payment channel (where the other side is receiving each transaction). That's how the "payment channel" concepts work.
Bitcoin can be used for other reasons beyond payment system transactions; for example, a bunch of coins are stored in cold wallets, as a physical store of value which cannot be confiscated. Market fluctuations still happen but that's unrelated to physical coin storage.