Mandatory meaning required features of a medium of exchange. Mandatory right now as in they exist right now because there is a demand for these features and there always has been and probably always will be. Not sure how to explain it further. I feel like we're wasting time with the obvious.
I see where you might be getting confused. I should be more explicit and say that it is mandatory now because it exists now in the existing, widely adopted, current
fiat system. I wasn't meaning that it exists already in crypto