The problem I think is, that although duality provides functonal/practical support, when it comes to verbal communication and understanding there is a psychological gap between duals. This gives such a relationship a kind of emptiness.
In my opinion verbal communication and understanding is better between identical relations.
The question is, what does a person want more in a relationship - a person who understands them or a person who provides functional/practical support.
I beleive that people want someone who understands them rather than functional support. In additon a relationship of functional support does not fit into the western concept of a "personal relationship" IMHO, unlike a relationship of understanding. In a dual relationship, you don't feel that you are in a relationship, rather you just feel that your weaknesses are being relieved. Your dual is your subconscious shadow who does not consciously understand you.