There's a lot more to atmospheric planets than just blue skies. Because once we can land on any planet with atmosphere, there is no in-game rational reason why we couldn't therefore land on every planet with an atmosphere. Including the complex life-bearing ones with trees, animals, and people. Being able to land on a non-terraformed-Mars-like planet, or on Venus, but not on Earth or any other Earth-like planet, would be both illogical and incredibly disappointing for the "we want atmospheric planet landings" crowd. So to make atmospheric landings good and realistic, they have to consider and invent solutions to all the complexities that creating a similar-to-Earth-like-planet would create:
- Weather. We're starting to see some weather-like phenomena with the "anomalies", but weather is complex. Wind, rain, clouds, dust storms, fire-tornadoes, the-flash-evaporation-of-entire-oceans-when-the-sun-rises and whatever else might exist in the entire universe of atmospheric phenomena. Right now, the only "weather" these planets have is clouds, and those are static. Next time you visit Earth, check out Greece. Except you won;t be able to see it, because it's got a giant storm hovering over it. It always has had this storm, and always will, until atmospheric weather gets an improvement - which presumably won't happen until Earth becomes landable.
- Water. And not just water, but other liquids: ammonia, methane, superfluidic helium, liquid silicates, molten iron and whatever other liquids might flow, pool and form bodies of liquid on the surface of planets in the ED universe. Making realistic creeks and rivers is tricky, and lakes would require additional programming as currently, lakes can only exist at sea level (as can be demonstrated by trying to find the Great Lakes in North America on the ED-Earth). What should our ships do if/when they try to "land" on an ocean? Do they float, or sink to the bottom like a submarine, or just explode like they did back in FE2/FFE days?
- Life. We've already got some simple, vacuum-tolerant lifeforms. Now let's cover entire planets with them, rather than just plonking down a small patch of several square km on an otherwise barren world. Right now, there's only, what, a couple dozen different lifeforms in the galaxy? That's the typical ecosystem of one tiny island on an Earth-like. I don't think there's room in the Codex for the thousands of different lifeforms you'd need to categorize to make just one ELW anywhere near "realistic" lifeform-wise, and there are billions of ELW, WW, AW and other life-bearing planets in the ED galaxy, each with their own (presumably unique) ecosystems and lifeforms. I don't think anyone would be happy if we get ELW landings and there's only four kinds of animal and six kinds of tree on the whole planet.
- Inhabited planets. How do you deal with the human settlements on high-population Earth-like planets (including Earth itself) in such a way that is both (a) realistic and (b) prevents players from going all Carmageddon on the local populace? Those planets can have billions of people living on them - just look at all the lights from their cities which we can see right now on the darksides of inhabited ELWs. We've got to be able to see those cities, up close and in daylight.
Then there's how these things interact with each other, and your ship. Do surface starports close down when bad weather blows in? Do the bird-analogues fly with the wind, or against it, or stop flying altogether when the wind picks up? Do the flower-analogues bloom a few hours after it rains? Do the tree-analogues tend to grow taller and more numerous along the creeks and rivers? Do the lion-analogues stay away from the Human cities?
Finally, a practical aspect: what should be the limits of landability, in terms of temperature and pressure? We should be able to land on Earth (1 atmosphere), or Titan (1.5 atmospheres) or even Venus (90 atmospheres), but probably not a planet with thousands or millions of atmospheres of pressure. Likewise temperature: there should be an upper limit, beyond which our ships and SRVs simply can't function.
We assume they're still working on all these problems, which is why we haven't seen atmospheric landings yet.
