@Riger I suspect the others can also bond servants/cards to themselves, but probably through different rituals (and the servants probably must have slightly different motivations).
The rankings seem to be divided in a way along how tarot decks lesser arcana are divided (the four suits in a tarot deck have four face cards each, and they're the ones that have a knight and a page instead of a jack).
So probably everyone can get cards, but probably only MC gets them as a harem (and some major arcana might possibly miss out, but Emperor/Emperess/High Priest seems like arcana whould should also be able to handle personal servants).