When sending ARDR, child chain tokens such as IGNIS or any other token to a new account using the new account's address the resulting account is protected only by 64 bit account id, which is somewhat not as secured as the 256 public key which provides ultimate protection.
The risk is that someone can brute force a passphrase that maps into the same account id so that both accounts are indistinguishable so that the attacker can spend the funds in this address.
More specifically, the reason why this one-time extra step is necessary is because the 8-byte account ID is much shorter than the 32-byte public key it is derived from. There are many secret passphrase/public key pairs that reduce to the same account ID (2^192 keys). But once a particular public key is associated with an account ID by storing it in the blockchain, no other secret passphrase that generates a different public key can access that account.
To protect against this a simple step has to be taken to record the account public key in the blockchain. Recording the public key in the blockchain protects against the attack described above.
You can donate to "Announce your Public key" service by sending coins to the following account: ARDOR-MVX8-RE46-YUFW-5FZSL. All coins go in to "Announce your Public key" service.