When I was transitioning I did a v. small standing order first for a few months and used it for spending, then upped the amount, then eventually switched over salary, direct debits etc.

This was a habit that a lot of us had taken, and as described above, it was just easier to do all in one place: - Go check your monzo app - Notice you're low on fund - Top up using your card

A lot of us haven't switched completely, because why would you when other current account can give you travel insurance, small % of interest, etc.

This is incorrect - it was possible for a long time to top-up via bank transfer. Certainly during beta. It simply required using a shared sort code/account number with a specific numeric reference which tied the payment to your account.

It wasn't as instant as it is now (with Faster Payments), but it was still definitely possible.

I used to use it all the time while traveling, and usually top up on the spot when the funds on the account run out and I needed to pay for something.

Bank transfers really doesn't work for that use case.

Now I'm using Revolut for the same purpose (they still allow card top ups), not much difference to Monzo although I really, really like Monzo customer support.