That isn’t to say that I think you should be stuck in a long with undecorated walls, because that might be a little creepy, and perhaps claustrophobic. I’ve been in an inside cabin in a cruise ship, and I get the concept of the window. It’s very comforting that you can see out, even if you aren’t going to be able to actually open that window – and let’s face it, you can’t open that window in the plane.
While I am not an engineer, and I have no formal training as to the psychology of the windows themselves, I have to imagine that having windows is less structurally sounds that not having windows. So what if planes didn’t have them, at least in the passenger compartment? Yes, this would make a giant steel tube, and it might seem claustrophobic. Hear me out.
There is plenty of technology out there to provide useful options to make it seem less so. Simply look at the Disney cruise ships for one such solution. They have created “magic portholes” in their interior cabins, where instead of a curtain hanging over a wall to make you think there is a window there (a process which really doesn’t work), they have an actual porthole installed over a computer screen. This can project images to show you the outside. Maybe it is a video of the outside, or maybe you watch movies – it doesn’t really matter. The point is that it is distracting you from thinking you see a solid wall at that point (and you also save space in a cruise ship, but that isn’t the point here either).
In a plane, you have lots of options – the “porthole” could be automatically tuned down for night flying, so some inconsiderate folk would not ruin the ambience when flying at night. If you are flying over something particularly scenic, it could show everyone, no matter which side of the plane, the same view. No more “those on the left, look here”. Instead you no longer miss the Grand Canyon because of a bad seat assignment. Now you get to see it. In fact, you could even zoom in. Heck, you could even use a smartphone-style zoom feature to get a close-up view. And I’m sure the airlines would love to sell you this as an add-on too.
If you don’t want to look at this “window”, just watch a movie. Or the in-flight progress. Or turn it off and see birds fly by (similar to Disney’s concept).
Whatever the case, not having the window, and the required holes in the hull, would seem to make a lot more sense from a structural standpoint.