For me this is simple, I only went along with a bride wanting free seating once! and I would never do it again.
There are two stages of your wedding where you need to think about seating the ceremony and the wedding breakfast, and both are equally as important.
Wedding Ceremony
This seating depending how traditional you are weather you have sides for your guests seating, but with modern times a lot of the guest may fit into both sides for example work colleagues if you work at the same place or some friends if you knew them before you were a couple. Therefore most people like to consider free seating but this still need to be considered with some allocated rows.
Gernerally people reserve the first few rows to ensure their parents/ grandparents get a front row seat, and also to make sure that onces you wedding party reach the front the have a seat and don't start walking around looking for a seat. This working can be reliant on the Ushers being around while guests are seating but can also be as simple as putting a reserved sign.
Wedding Breakfast
This is where I went along with a bride once and will never do it again!! Here are some of the issues which happened:
Family members were on the furthest away tables while work colleagues were sat next to the top table.
Seating took longer than allocated seating as people were confused.
Couples got split up as there was only 1 seat left on the table
The last few guests had the award situation of trying to find the last few seats.
I know doing the table plan is probably the most stressful part of planning the wedding, as there is always guests which you don't want to seat near each other or there are too many guests to fit on the table how you would like them too, but after witnessing this situation I personally would never do it again.
One way around the full allocated seating is to allocate tables so people are free to seat where they like on a specific table which is sometimes nice and also slightly easier for the couple making the table plan. but when doing this you need to consider the caterers as if you have a lot of dietary requirements guest would be harder to find but not impossible.
You might be thinking, you wedding is a casual buffet which is great but if you have enough seating for everyone to take a seat and everyone is eating at the same time a table plan is required, the only time I would say you don't need a table plan is if you have a buffet with no specific eating time, so people are just coming and going as they please.
So there it is a simple short bit of advice on seating, now hopefully before you decided the table plan is too hard you will think about the drama that might unfold on the day without one.
If you are stuck with your table plan this is something I help with for my full planning couples and all my couples receive an allocation sheet.