Well, some people are already doing that. People earn in bitcoin and spend it on fiat. Go to cities with lots of bitcoin atm machines, and you'll see the most obvious way people use btc in their daily life. Maybe one day, when it gets popular, it will be widely used. Even if it's just widely adopted in the internet, ill be happy about it. No more trusting 3rd party establishment in doing transactions in the internet!
It's slowly in the process of being widely adopt within the internet. More and more establishments are starting to accept bitcoin and it's popularity is increasing. Some people even have jobs by earning bitcoin and they therefore use their earnings on a daily basis. They would have to convert their btc into fiat first before using it because bitcoin cannot be used as payment in many places. This way, it's being used in their daily life.