[lonesword]

Genuine question - why assign seats at all? In my country (weddings with 200+ people are the norm) people sit wherever they want. In the US, you wouldn't assign seating at a house party (right?), so why do that for a wedding, since a wedding is after all just a more expensive party?

[veddox]

To allow different circles of friends to sit together.

At the weddings I've been at (usually 100-150 guests), there would be families and relatives of the groom and bride, then their school friends, church friends, university friends, etc. - anything up to a dozen different groups of people who know each other but not the other guests. So a seating plan allows these friends to enjoy the party together. It doesn't prohibit them from getting to know the other guests, but offers a bit of a safe space with people the hosts know they will get along with.

(Additionally, in many cases, these groups of friends may not have seen each other for several years, e.g. since their school days, and appreciate the opportunity to catch up.)

[n4r9]

Weddings are usually somewhat formal. Formal events benefit from guidance to reassure guests. For example, a dress code helps you narrow down your choices if you have no idea what to wear. Similarly, a seating plan is great for someone that is there on their own and has no idea who they can sit next to.

The trick is to combine guidance with a relaxed atmosphere where it's fine to ignore it. Your dress code might say "black tie", but it's great if someone turns up in jeans because that's what makes them comfortable.

[couchand]

To add to what others have said, a big part for me is that you're asking folks to come. For the most part the social expectations of guests are pretty light: watch this quietly, light mingling and chatting, clap when it's time. Sitting down for a meal is unique in that guests must have a sustained social interaction with other guests.

[teejae]

As others have mentioned, this is very culturally dependent. And culture isn't necessarily country or region. Different types of people like different things. This particular app is designed for those times when you need more assignment, for whatever reason.

Hope that makes sense!

[hermitcrab]

This varies a lot from country-to-country[1], by 'social class' (for want of a better word) and event type.

[1]And even within countries. I believe it varies from state to state in the US.