I'm a Monero supporter (and owner and future user once more widely adopted) because like cash, no one can tell how much money you have in your wallet or who you're buying things from. With Bitcoin, neither of those is true.
How much money is in my Bitcoin wallet?
If you watch for long enough, you can wait for a transaction that spends from the address you know, and you might find some other addresses that were spent with it.
It's true that a non-zero amount of information about your Bitcoin holdings is leaked. But it's not true that that amount is 100%.