Why aren't screens round instead of rectangular?

X-Y addressing and raster scanning are both much simpler when addressing a rectangular area. So either you need to lose (waste) the corners or adopt a fundamentally different addressing scheme.

There HAVE been polar displays on round screens so it's not impossible - just very inconvenient... look at 1940--1950s radar screens for some examples. Maybe some vector graphics displays in the 1970s, GEC 4000? but my memory is hazy on those.

I have failed to find any 1970s vector graphic displays with non-rectangular screens, but this slightly NSFW image from 1956 shows that round CRT displays were not exclusively the domain of polar plots.

Presumably radar practice influenced the choice of display on this project, which may have been a polar plot at heart, augmented with information drawn in vector graphics form, and therefore not bound by the regularity of raster scanning. The linked video (IBM Sage Computer Ad, 1960) doesn't actually show any polar plots, just vector graphics and a precursor to touch screen interaction.

The earliest CRT displays were in fact round. However, that was more due to manufacturing tradeoffs of making large glass envelopes with vacuum inside than a desire for the display area to be round.

Rectangular makes more sense than round for a variety of reasons:

1. It's what people want to look at. We use rectangular pieces of paper. Photographs are generally rectangular. Contrary to what you say, we don't perceive our world in a visual circle. Our visual attention area is wider than tall. Consider that rectangular paintings have been the norm from the beginning. Sure, circular paintings exist, but far far more of them are rectangular. Especially when each canvas was made by hand, the artist could have chosen pretty much any shape.

2. Rectangular shapes are easier to handle. Imagine if all the papers on your desk were circular. They would be difficult to stack, file, and above all, line up a stack together. When manufacturing a frame for something like a picture a rectangular shape is easier. Rectangles can be tiled with no gaps, whereas this is impossible with circles. Building circular windows in houses would be more difficult and labor-intensive than the rectangular ones we use now.

   Rectangular frames of various sized can be built from the same linear stock, just cut to different lengths. With different circular sizes, lots of different curvatures would need to be stocked. Linear shapes are much easier to saw, extrude, etc.

   None of this says why display screens should be rectangular, but when everything else has a good reason to be rectangular, then having display screens circular would be annoying. You want to be able to go back and forth between display screens and the rest of the world that works on rectangular visual snippets.

3. Rectangular devices have orientation. Something like a circular smart phone would be a pain since you'd always pick it up at some arbitrary orientation, then would have to turn it to get the top up. Yucc.

4. Having a narrower and wider dimension can be useful. Think of a cell phone in your pocket. Pocket openings need to be kept narrow, else things would fall out too easily and there'd be other undesirable tradeoffs in the garment. Different limitations apply to pocket depth. The result is that pockets are usually deeper than wide. A circular cell phone, for example, would be limited in size by the pocket width. A rectangular cell phone can have more area by allowing the long dimension to be wider than the pocket.

5. Pixels are arranged in a rectangular pattern. This simplifies manufacturing arrays of pixels, like in LCD monitors, and results in the simplest math we have come up with for addressing pixels in software and physically addressing them electrically. When images are rectangular-aligned arrays of pixels, it naturally follows that images are rectangles too.

   How do you propose arranging pixels in a circular display? If you leverage the existing manufacturing technology, then they will be in a rectangular pattern, but with awkward short rows and columns at the edges. If you lay out pixels in a circular pattern, you will have to develop all new manufacturing technology, and the software and hardware to address them will be a nightmare.

Rectangular displays make sense. They were not chosen by laziness or arbitrarily. They are what you inherently want.

I think you can take this all the way back to photography, film was always shot square because its more economical, you waste less film, and your developing paper is also cut square (Think about cutting cookies out of cookie dough, theres a lot of waste) To enjoy a round display you'd need round format media. There are quite a few reasons you wouldn't want to film in a round format You'd need larger film reels, the projected image would be smaller to fit on the same size film, and it would be harder to frame your shots and exclude extra stuff from the shot.

The eventual driver of screen development is media consumption, and since all the preexisting equipment is set up to use square or rectangular formats the need for a square display becomes more obvious.

In other words, while we may have developed and could have continued to develop round screens, there isn't much that needs to be displayed on them in the mainstream.

The physical efficiency, convenience and simplicity is probably the right answer. But yes it would be better to have a big oval wider on the sides screen to watch videos because how our eyes sees the world. You can ask the same question about our writings. Imagine instead of letters we had organic looking shapes and patterns like the aliens in the movie Arrival. Our brain could've understand it much quicker because its a master of pattern recognition. But we are not that smart as species yet or just took another turn in our history. So we made everything as simple and efficient as possible. But who knows maybe we're just not there yet. Maybe in the future, how far that might be, things start to change to form a more organic shape. Somethings that our brains and sensors are naturally evolved to work with. There might even be no need for screens at all. Softwares and media might start to consider natural human vision to display things as VR and similar technologies evolve. There might be no need for reading to get information, as likes of Elon Musk are trying to widen the bandwidth between our brain, AI and the world. This might seem like forever for us, but it is just a tiny slice of time we're living in. Can't even imagine life in 50 years from now.