Well for one thing, the speeches about the groom are usually made by men from his circle of friends, and likewise for the bride and her friends. I wish I knew why this is, but I've repeatedly heard, mostly in psychology class, and occasionally noticed personally that ribbing seems to happen far more among groups of men than it does among groups of women. I've got female friends who have ended friendships over insults from their peers. I'm not really sure why that's the case. Perhaps if there was a wedding with a bride, who invited friends who were more comfortable with insults, then the two speeches would sound more alike?