Websites already get informed if your phone is set to dark mode, you can darken your page with just CSS. So you don't need actual access to the light sensor for

Websites already get informed if your phone is set to dark mode, you can darken your page with just CSS. So you don't need actual access to the light sensor for that, and in fact you probably shouldn't use it for that... since you might be overriding the user's dark mode preferences.