I guess people will start loosing their interest on btc most especially on small or less fortunate countries. Because if btc to fiat exchanges will be ban most likely it will be on this countries. Even though btc is important for us, not all people accepts it as payment or government accepts it to exchange with fiat. Every country need money, so if they don't know about btc because they're lacking, then it will be hard for them to exchange it with fiat. Also, users will either stop investing on btc and block chain will be use in other applications.