The only disadvantage of bitcoin at a moment is that its usage is very limited and even after having bitcoins in our wallet we cannot use them anywhere like fiat money and that is the biggest drawback of bitcoins.
bitcoin is not actually for that purpose according to my assumptions. i think mostly people from all around the world use it for investment purpose. they sale when price rise and purchase when it goes up and for sale and purchase of goods you can use it but it is accepted every where so, its better to use fait money for that purpose.
I agree with you. As of now bitcoin is not that like the common currency like dollar that we can use everywhere and well known anywhere but bitcoin is just a new cryptocurrency and many people didn't know bitcoin so a lot of people that is interested to bitcoin doesn't have a choice but to just invest in bitcoin because they can't use it but they can hold bitcoin for a few years and earn money and just use it until bitcoin is widely accepted.