This is one of those questions the I’ve asked many a time and am still not 100% sure of the answer.
The purpose of a significator card in a reading is to focus the energy of the remaining cards on the questioner or querent. With the current deck that I use, a significator is almost pointless because the only energy to have touched them is my own, but if I were reading for others, I do think that I would have them choose a significator from the court cards.
This goes more toward my own style of reading tarot, which is semi-detached. I wouldn’t tell the person that I’m reading for what the cards mean or what the descriptions are other than the general stuff simply because I feel it works better when they feel a card drawing their attention. Alternately- I don’t want to know what your question is. My job in a reading for another person is to interpret what is being said by the cards in the spread and if I know what you are asking- OF COURSE MY ANSWERS WOULD CHANGE! I don’t charge, nor do I read for many people, but for those I do- I do not want to put my opinion into their thoughts.
I do feel that one of the primary benefits of the Tarot is that the cards are based on archetypes. Part of what I enjoyed about reading Carl Jung’s theories was that of the universal subconscious and the archetypes of all humans. There are necessarily generalizations that can be made in the world and the cards represent what you want to see in them and they are general enough to fit most any realization you need to come to.
I’m not saying that I don’t believe in the more mystical aspects of Tarot, but I do tend to focus on the practical. If something is bothering you and you ask your cards for an answer, then as you are laying out your spread you find out that The Tower is crossing you. This does not mean that the future is being told, it means that you will now try to think about what that card may represent. The archetypes in essence remind you to think about all things that effect a situation or question and to open your mind to a different answer.