People in countries with shady governments and broken economies have higher likeliness of using Bitcoin and stablecoins. Most countries are simply in not that bad of a situation so they think they don't have the need to use them.
True, these.
But also education. The vast majority of people don't have a clue what bitcoin is, why people like it, and what its used for. They also generally think its a really bad thing cuz that's what they've been told. It's also kinda like the olympics so far, once every four years they hear about it, except the rest of the time they just assume it died and that last bubble was its last breath before death. Until people get that bitcoin isn't going away, and they get that it isn't some bad thing, they won't have any desire to become educated on it. Education of the masses is gonna take decades because there is so much continuing misinformation and irrational hatred of bitcoin in the public sphere, and because as you say, in most countries fiat is mostly perfectly fine so they don't see why something different is needed.