At this stage bitcoints not so popular as the dollar. But its popularity is growing. By dollar just all become accustomed. A cryptocurrency a relatively new and many people do not trust it
People massively using the US Dollar doesn't mean it's more or less popular than currencies such as Bitcoin.
They use it because there is no other option than that in their daily lives.
I don't ever think people (non Bitcoiners) will fully trust or believe in Bitcoin as a currency since there is no central authority.
The US dollar is much more popular than the bitcoin as the user numbers of the US dollar is much larger.