In Europe, sleepers tend to be shared up to the occupancy limits of the room....and so strangers of the same gender may be booked into the room if the space is needed by the railroad (if one is paying the "double" or even "triple" rate, then one must be prepared to share accordingly, while paying the "single" rate will result in exclusive occupancy).

The U.S. has long considered this practice quaint, and there is exclusive occupancy per room...and pricing is by room rather than by bed....(the "coach" fare is always also paid by each person).

As far as the diner is concerned, sharing tables is just an American tradition, for better or worse. As most have pointed out, it is usually for the better.