Because of cultural reasons
Answer:
religion
as it links to ethnicity as well
other people might be following this religion
I'm NOT 100% sure about this answer but I think it's the Lines of Longitude
Tectonic plates are parts (pieces) of the outermost layer of Earth: the Crust. (the outermost part of the mantle is also often included in the plates). This means that the land in the middle of the plates is relatively stable while the borders of the plates can be in movement - after all this is where two pieces meet. Plate borders are where the vocanoes and Earthquakes often take place.
I’m assuming you’re asking about the moon, if correct, here is the answer: In bright half , the bright part of the moon increases whereas In dark half , the dark part of moon increases. Bright half starts from a new moon day and ends on a full moon day whereas dark half starts from a full moon day and ends on a new moon day.