Yeah you are right but you're forgetting that they also recommend that they also have separate accounts as well as a joint "household" account. Remember around 50% marriages end in divorce so it's basically a coin flip.
Yeah, but when a significant number of that 50% is due to finiancial issues, it's not so much about the flip of the coin as it is about the coin itself
Look at it this way:
Why would you need a separate account? Don't trust her with your money? She doesn't trust you with hers? It's usually an underlying trust issue in the relationship that causes the 'protect what's mine' instinct.
If you trust her implicitly and without reservation (which you should if you've committed the rest of your life to her), then what's the issue?