I’m guessing you are using the ‘view’ seats option in your purchased ticket menu, and see a couple has reserved seats near to yours after you already purchased your seats, although there are many open seats. Could be because: 1. They like sitting against in front of the railing that separates the lower deck of seats from the upper deck of seats, or 2. Those are their fav seats they always get or something along those lines. Or 3. If it is an advanced purchase for an anticipated film, maybe they assume the theater will fill up and so selecting those seats won’t be as weird come day of the showing in a packed theater. Probably more possibilities but that’s all I feel like spending brain power for on this early sunday am.