The issue is that by the time people in those countries realise their currency is devaluing, it's too late, they can't really afford to buy much bitcoin. You really need to diversify into bitcoin in the good times before the s**t hits the fan.
What if such countries decide to adopt the US dollar (or any other global global liquid fiat) as their currency when theirs get devalued, in the place of cryptocurrency that they are hesitant to accept?