Yeah, because if their first scene after the marriage was another threesome of them with another woman you'd all have a major issue with it?
Seriously, in practical terms, what difference does that actually make? They were already living together, and had a child together. And yet they were still bringing other women into their relationship. They even shot porn while she was pregnant. At this point marriage is a technically, I don't know why they chose to do it now, but how does that piece of paper make this any more shocking or scandalous?