Why do teens love dark mode ?

My son is 14 he'll be 15 in December he uses dark mode on his phone all day I don't see how teens stand it it hurts my eyes especially when the sun shines on the screen you can't see it well. iPhone dark mode seems to be brighter than Samsung which I don't get why one phones dark mode be brighter than the other we all use Samsung. My wife aka my son's mom uses the 7pm to 9am settings I use mine on sunset to sunrise. Why do teens love dark mode so much ? How can you stand it all day ?