The maitre 'd does try to match similar people. However, I don't think they put as much effort into it as they used to.
On my last Carnival cruise with my Son-in-law. We were seated with two families, with small children, at a table for eight. We asked to be moved because one of the families (the father and mother) were quite abrasive. We were then moved to a table for two. Oh well.
Over the years we've been seated with great people and the good seatings are far far more numerous than the bad ones.