Adding Custom passfrase ian coleman based method

Description:
One question why MetaMask wallet create the 12 words seed automatically but do not let you put a additional word (passphrase) like some bitcoins only wallet as electrum or sparrow , exist some limitation, MetaMask use bip 39 method? I think that Will be a improve in the protection of your wallet , would be possible to implement a option to create or to restore using a bip 39 whith passfrase option then really making your personal wallet, as example using Ian Coleman memonic site to generate you wallet, Sorry for the longe message and thanks for the time

Purpose:
Privacy and security

Extension/Mobile/Both:
all

Images/Attachments: