Money needs to be anonymous. When it is not, redemption and transfer will be given special preference based on who you are rather than an independent value. When you perform a transaction and its effects aren't solely the transfer of value or you even need to file paperwork to report it (!), you're not really dealing with money. When a transaction can be reversed after it's been made, you're not dealing with money.
And while Bitcoin currently has these properties in that a name isn't tied to a transaction, the blockchain is simply a list of which psuedonyms gave what to who. It lacks the important property of "untraceability" which prevents malicious actors from tying nyms to your singular government mandated identity (cf Chaumian tokens) and therefore implementing these "features".
(And for the inevitable response, no, ad-hoc mixes are not a solution. They force the attacker to be active (eg pass laws) instead of just passively watching. When untraceability doesn't apply unconditionally to every transaction, then transactions which attempt it will be gradually more frowned upon. It's not hard to envision a future where types of Bitcoin users are progressively forced to register their wallets).