This type of discussion always fascinates me (I’ve had it with friends as well).
Because my wife works part time (to do the school runs, save on 4 billion pounds worth of childcare), we don’t have a situation where my money is mine, and her money is hers.
It all goes into one pot, and we just take from there.
But I have many friends who are in relationships where they both earn similar amounts, and it’s more of a case that whatever is left after the joint bills, is theirs to do with as they please.
I guess in the latter scenario, your personal Monzo account would be used more.
But for us, and anyone in the former scenario (I’d guess at least @glasgow was in this bracket as well), the personal account simply gets neglected as it serves very little purpose.
I had initially thought the majority of people using a joint account would do it this way, but from reading other comments, it doesn’t actually seem to be the case.