Until another data breach of a service where you have your card remembered (like Ticketmaster recently).
Preventing it would save time and effort for both sides and potentially a lot of money for Monzo in case of fraudulent transactions that cannot be reverted (e.g. ATM withdrawal)
That’s a risk you might or might not want to take. Again it depends on the use case - I rarely fall for such sales and rarely have no data/signal/battery.