The hardware to create a convincing effect is simply too expensive at the moment to be mass market. You can produce collimated light with either a reflector or

The hardware to create a convincing effect is simply too expensive at the moment to be mass market. You can produce collimated light with either a reflector or a lens but both have their issues. Reflectors will add required depth to the package although it can be minimized to some extent. This makes for a rather bulky install and isn't something you can just hang on the wall. Lenses allow the design to be flatter but the more easily produced fresnel variety won't have the same quality of light. You also have to balance whether to use a single point light source or multiple sources and reflectors/lenses. Cooling becomes a problem for light sources that are bright enough to mimic daylight, this would also add noise which would break the illusion of a window. You need a diffuser of some sort which adds more cost even if it is just a sheet of plastic. All of that adds up to a fairly bulky and expensive piece of equipment which is why you only see a few high end companies producing them for a very niche market. Hopefully this can be changed in the future by having the cost of high power LEDs come down even more. Maybe mass production of high quality lenses will be helped by developments in the VR field. There are some promising developments there with so called pancake lenses that could make things a lot smaller.