I suppose for bitcoin being a property is also a sensible thing. Because if bitcoin is an asset, its value will be determined by the law of supply and demand, and if it is currency, it will be subject to many legal frameworks of government.
Bitcoin in its nature is like the two faces of a coin. It can be seen as an asset and also as a currency. Either ways has it own advantages and disadvantages. As said, if Bitcoin is considered as a currency, it makes it liable to government regulations such as payment of taxes with each transactions and other authoritative suggestions. On the other hand, being a currency grants Bitcoin the ability to serve as a medium of exchange.