Go to any local supermarket and see which currency they are completely comfortable with. It is always cash and will be cash for at least a hundred years in the future. Digital payments have go up but it still uses the same fiat currency in the background - just that the payment method is easier and you would not need the cash physically.

In such situations bitcoin is least known in some countries but might be popular in few, but it is not so in some. Things might change in future, but we only represent a small subset of the world's population.