Not surprising that they haven't heard of it. None of my family members know much about it either except for the fact that it has some value. The only people who follow the internet news would have likely heard about it. Its very rare to have a new article about it too.
Yeah it is true that only people who are using the internet have likely heard about bitcoin. Here in my country, not all people here have the access in the internet. And not all who access the internet have the knowledge about bitcoin. Maybe for now, many but not everyone has already known bitcoin. And maybe it will take more years for bitcoin to be known by everyone in this planet.