Why is a circular smartwatch display so hard to make?

[Kaaxi]

Is making a circular display hard really that hard to produce? The moto360 has that small cutoff on the bottom, but the new LG Watch R claims it will have a full circle. What's the deal with these... anyone know?

[Martau5]

The problem with making a round display for a smartwatch is the OS and pixels. Adapting Android or iOS for a new screen size would be a ton of works. This happened when Apple made the iPhone 5 longer. Also the content and apps is made for square or rectangle screens, so everything needs to be created from the ground up.

I think Apple could make one round but sounds like even they are running into production issues with their smartwatch.

[SmartWatchr]

There is a thread on Quora which explains why. Little bit less technical explanation:

1. Smartwatch LCD Screen design
   The design of an LCD display has been traditionally made for rectangles or squares (TVs, phones, tablets, etc). You need space on the edge of the display either on top, bottom, or sides for the components that connect. A smartwatch with round display gives little room for that. That's why the moto360 isn't a full circle display

2. Manufacturing a Smartwatch circular display is difficult
   With a circular display you cannot do a smooth linear cut of the glass and you have to cut along a path. This means during production you have to produce more than one screen to get a working screen panel, which adds to production costs.

3. P-OLED
   However, building a round device with a round POLED screen is more feasible than using glass. Plastic OLED allows to create custom shaped screens much easier because the panel doesn't suffer from the mechanical stability when cut differently, and the wiring of the individual pixels can be done in a smaller bezel.
   However, the first POLED-based product has only been commercialized this year, the LG G-Flex. So the technology is still really expensive.

4. Smartwatch Resolution
   To have a good smartwatch LCD display means you need a resolution at least above 300ppi (pixel-per-inch), which is driving the price further up, for a market (wearable tech) that is considerably small as of today

5. Smartwatch Touch Screen
   A touch panel consists of very fine vertical and horizontal wires going across the screen. On a rectangular screen they are running down the sides into one direction. On a circular screen they would have to run circular along the side, on top of the display, adding further to the overall size of the Bezel around the screen, and also adding potential interference to the signal.

6. Everything else needs to be round!
   When designing such a round device with a narrow, round bezel, all your components need to fit in there as well. Currently most components are designed for square devices so this is very hard to achieve. There's very little smart in a Smartwatch so you need to pick and chose what goes in it.

7. Smartwatch Apps, Software, operating system
   There was no existing software that can be used for a round interface until now with AndroidWear offering a versatile framework to easily develop a round device without having to bother much about UX and interoperability.
   Until now you had to develop it completely on your own, including the UX that goes along with it.
   Another significant cost-factor to consider when designing such a device, because given the price you reached already for the hardware, you need a software which is very functional and also compatible with a wide range of devices and applications.

This list is not complete, there are several more items to consider, but I think you get the idea.