You don't need mass adoption to be useful, the more adopted a currency is the more useful it becomes but it's not binary. Seychelles has a population of 130k, does that mean that the seychellois rupee is useless? Of course not, 130k people use it everyday.

~100 milion people use or at least own bitcoin, meaning they would probably be willing to pay or accept payment in it, that's 1.3% of the world's population, 1 in 80 people, that puts bitcoin between the Japanese yen and the British pound. ~260 milion people use crypto currencies in one way or another, over 3% of world's population, 1 in 30 people, that's just under the euro or the us dolar. And if you use 1 crypto you basically know how to use them all, just like €,$,£. If that's not mass adoption I don't know what is.

Most merchants who accept ₿ also accept other cryptos like ethereum, stable coins, litecoin, monero, tron, bitcoin cash... There are payment gateways that make it incredibly easy and automatically convert to your currency of choice, so there is no reason not to accept even the shittiest of shitcoins if it will be swapped before it even gets to you.

Great points!

Or if you need it for some other particular application, like drugs on the dark web.