Sure, but having the bitcoin sitting in the bitcoin wallet doing nothing makes it kinda worthless, yah? The whole idea is to use it for commerce, at which point you are vulnerable to all sorts of scams and theft that you would normally be protected from.
Then there's liquidity. Most transactions are off-block-chain (as in one block-chain transaction per every ~400 or so off-block-chain transactions). They have to be, because putting a transaction on the block-chain takes too long. This means that you must inherently hold a balance, in bitcoin, with a third party, if you actually want to be able to use your bitcoin for general commerce. There are currently no protections whatsoever against that balance.
And then of course there's the volatility of the buying power of bitcoin itself. It's one of the most unstable and volatile currencies in existence.
That said it is better than nothing and certainly better vs certain emerging market currencies undergoing hyper-inflation.
But it isn't better than the dollar or any western currency and never will be.