Woman loses thousands of dollars to romance scammer posing as astronaut in distress

There's two barriers to that. Banks don't want to reverse transactions without a court order, because they would then be very embarrassed and also get sued if the transaction turned out to be legitimate. So they can reverse transactions, but only after the court orders it.

The other thing is that scammers know that. This is why they often demand payment via Western Union, gift cards, etc. They also often use "money mules": other scam victims who take the money and then send it to the scammer's account, taking a cut. The scammer periodically closes accounts and opens new ones, so if their assets get frozen they don't lose too much. (The money mule scam victims are sometimes just being conned into helping the scammer, but sometimes they end up getting scammed themselves, such as by being sent bad checks. They can't go to the police because they're guilty of a crime.)