Security, the weak point of brainwallets
Security and lack of entropy is what makes brainwallets weak. You could think at the time of creating your wallet, in a phrase that you consider unique, but in this world of more than 7 billion people, it may be the case that you are not the only one who has thought of the same thing, with the same words , and try it with a purse. Probably that is rare, but highly possible.
The problem increases even more by our own nature, we are beings with great memory capacities, but if we do not use that word or phrase repeatedly, we will most likely forget it. Faced with this fact, what usually happens is that we use the same patterns to secure things of value, which leaves us at the mercy of any social engineering attack, and that would lead the hacker to steal our keys. Do you see it unlikely? Well, tell the millions of people around the world who use the letters "qwerty" "dvorak", "1234567890" or their DNI number as their email password. Cases like that are not uncommon in the computing world, and if we bring it to the crypto world with brainwallets we will see the same pattern.
It is not uncommon to think that someone comes and uses a Psalm (yes, the biblical ones) for the seed of their purse, or the phrase of a famous actor or song, they are simple ways to remember things that are important to us and help us protect values in certain scenarios, but in crypto, this is dangerous. In fact, it is enough to put a small GPU farm to attack this type of wallet and succeed, and the result of this would be that of large numbers of people who would not understand how their bitcoins have disappeared from the wallet, believing that Bitcoin has a problem, when it has nothing to do with Bitcoin.
Hence, cryptocurrency developers always aim to use seed phrases as designed, because they provide a great entropy in each case and, therefore, no wallet will be the same as another, and only by backing up your seed, you can recover access to your coins quickly.
Given this scenario, our highest recommendation from Bit2Me is: AVOID using brainwallet wallets to keep your cryptocurrencies safe. Instead of finding a safe place for your holdings, what you are doing is creating a weak and cryptographically insecure space, which others with some work can break.