What is the natural science reason to wear blue light eyeglasses instead of just turning one’s computer display’s blue lights off or very low in spaces where there are no other sources of blue light than the screen the person is watching? Suppose that the person has perfect visual acuity without eyeglasses. Suppose also that all other possible protective measures achieved by the blue light eyeglasses are achieved by other means, such as by using UV filtering eyeglasses of the same shape and frame material and frame color as the blue light eyeglasses assuming that the blue light eyeglasses do have such protection. Economic, ease of use, technical savviness, time needed to configure the display or other such reasons are out of scope of the question. Other situations where there is blue light are also out of scope just as the overall harm caused by blue light.
The reason is that the assumption ‘no other light sources aside from the screen’ is almost impossible to control for. You’d have to be in a room with no daylight coming in and zero other blue light sources emitting from say a smartphone, clock readout, artificial lighting for the room and/or any of its appliances.
Even accepting this ridiculous decision to rule ‘all other sources of light out of scope’ then the obvious only possible answer is that THE SCREEN EMITS BLUE LIGHT OUTSIDE THE CONTROL OF SOFTWARE COLOUR SETTINGS. For example, LCD screens use a white light bulb to light up a screen of LCD pixels. This white light leaks. It’s why LCD screens have lower contrast (black looks dark grey).