Why?
Well, the fact that we are glued to our seat, ie cannot move a muscle, except of course our head to look around, sort of puts a dampener on any activities.
What's the point of planetary landings for the sake of it?
This has been answered repeatedly by those who look forward to it immensely. Do you expect a different answer when asking again?
Let's say it's just airless planets for now.
Flight changes immensely. There is gravity. There is also a concept of altitude. Half your sky is solid and you can't fly through it. This is before even getting into canyon flight, low-level evasion, and what combat would be like close to a planet's surface. That's difference enough just by itself - suddenly we have an enormous number of new playspaces which are radically different to open space. Even doing the same missions in these environments (dogfighting pirates down near the surface) would bring variety by itself.
It may not matter to you, but there are an enormous number of people who want to see the landscapes of other planets - watch the suns set over alien mountains, learn the terrain of a moon in their home system, find a landing spot they love for its view. However you might want to dismiss that, this is what Frontier and FFE did
twenty years ago and there are
still people who adore the game just for that. And play it too.
Suddenly it isn't just open space we can play in - it's potentially every planet we see, each with its own terrain and characteristics. This is more than just an expansion of gamespace. It's a multiplication of gamespace on a whole other level. Now maybe that means nothing to you, but it's a very big deal to lots of people.
This is before we even get into atmospheres - which bring weather effects, changes to the flight model, cities, plants, life, animals...
To be able to fly down and see those things have worth, just by themselves, and even without ever leaving the cockpit, to the people you're addressing.
It's fine not having any interest in that kind of thing. But to act as if it's
nothing, to say that represents a complete lack of content? Are you really going to be surprised if people love simply being able to fly down onto planets for the sake of it? Are you really surprised that people disagree with you?