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.