Table numbers

I agree with pp. Even with a "small" group of people who know each other, they are not going to efficiently seat themselves into groups of 8 or however many your table size requires. It truly is MUCH better that you figure out which table to seat people at and let them know the expectation with a table chart or escort cards. Without assigned seating, some venues actually require the customer to plan for up to 25% more space/seats/placesettings/etc., because people will do weird things.

I've been to weddings without seating charts and it was fine because they did a buffet dinner. Didn't really notice or experience any of the issues listed in other comments. We were trying to not do a seating chart but got sucked into it because it is much easier to coordinate. plated dinner at our venue.

If you don't assign people to tables, you'll have to plan on having additional tables since guests won't break themselves into groups of however many seats per table. You'll also have to deal with people leaving open seats between them or not filing tables fully so they can stay with their group. That means more linens, place settings, centerpieces, etc., which will drive up your costs.