Neil Oseman has a great article from April on Is Modern Cinematography too dark?
An interesting read, though I don’t think it goes into a main reason behind much of the issue. The color bay. Color bays today use the absolute best top of the line equipment, the best and brightest monitors and it is done in a dark room. This method of color correction makes great results for the theatrical experience, where the lights are off, and it is a very dark environment. In this “perfect” situation you can make the image much darker than you maybe should, especially for a TV show.
If you are delivery for a home experience, you should use a lighter room, because that is what most people do at home. Heck at home I have my iPad half the time, so another bright screen. I hate when a show is so dark that you are forced to turn the lights off just to see anything (I can except it with a movie, but not TV).
Oseman talked about the Game of Thrones final season which was so dark it was a joke, and then concludes that it is what the cinematographer wants, but again they should then correct in ideal situations for how they are delivering.