When I’m reading for you, I want to make sure that we have the freedom to talk about whatever is on your mind or your heart. If your partner is present, you might not ask about something you really want to understand. This applies to issues in your relationship and in your life.
Also, when your romantic relationship is struggling, it’s easy to blame the other person for everything that’s going wrong, when in reality, the only thing you can control is your own thoughts and actions. If I were to read a couple together, one of you might feel validated by my feedback to support your point of view, and not examine your own behavior in the situation. That won’t resolve anything.
Example: couples often fight about housekeeping. One partner is messy while the other one criticizes the messy one. If I was to give them a reading together, the critical partner hears that their partner is messy while the messy partner hears that their partner is critical. What the messy partner needs to hear is that they are too messy, and the critical partner needs to hear that they are too critical.
That being said, if you get a reading and want to discuss at length after the fact, knock yourself out!