I would like to have multiple cards, with different amounts on them.
I’m happy to poke my card number into some untrustworthy website when I want to buy something for €60, because I never keep much more than that on the card. But because I use my Revolut card on any old website in the interwebz, I never trust that my card number has not been accessed maliciously.
For this reason, I never use my Revolut card for large transactions. But if I could have two cards (one could even just be virtual, I don’t need a physical card for it), then I could have one with a very large limit for paying for larger things, but which I only gave to very specific services.
I actually use a card from my bank, instead of Revolut, for large transactions, due to this problem.
It would also allow us to transfer large amounts of cash to Revolut and simply transfer the minimum across to our primary card whenever we needed it.