at being trendy like the dining in the dark themed restaurants? (Other explanations come to mind but I'll not go there -- I'm sure others may)

Larissa Pearla, a NYC beauty. Her incall would be pitch black, with just a few fake candles and I couldn't see a damn thing. So I got smart and all the future dates with her I wore my sunglasses inside the hotel and took them off just before I knocked on her door! It helped immensely and she would let me peel back a curtain to let some natural light in. Some women don't know, or forget, that men are visual creatures. Let there be light ladies! lol

She’s caught people trying to secretly film the act.

If that’s not a provider’s reason, then it’s probably because the burger doesn’t quite match the picture on the menu board.

If not, leave her dressed and hike her skirt up a bit.  Doggy may be required for a butter face.  

Virtual darkness?  Was it actually illuminated but the photons were afraid of something?

I had an experience sort of like that. Although I met her downstairs in regular room lighting, when we got to the room, she had me enter first and I snapped on the lights. She came in and turned them off. Huh? I told her that I wanted to be able to see her! But she insisted on lights off (except for some other dim mood lighting).
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As clothes came off, I think she wanted the lights down because she was concerned about flab, or cellulite, or a scar, or some other "flaws" and I put flaws in quotes on purpose.  Even worse, who knows if she might have had sores or some other more significant and important blemishes that she didn't want me to see. Sounds creepy, but I haven't had to deal with the dim light problem very often.

including me, you may prefer ladies in the 35-45 age category for the social connection.  Although most of these ladies are still beautiful, they may have minor skin blemishes, a few wrinkles or scars, as Jensen said.  Low-level lighting can eliminate their self-consciousness about such things, put them at ease and make you both feel young again.  For me, it's a positive thing, but my eyesight is still good.  Perhaps ask her to put out some candles or night lights around the room to give some additional background lighting.   If you can't get them to do this, then see younger girls who are 25-30.  If you want, they will fling open the curtains and put sunshine on your ass, because most still have fairly flawless bodies.  You just won't get the social connection you will have with a woman closer to your own age.  

Just an FYI regarding my last session.The provider is well reviewed on this site with almost all 10s or 9s for appearance.She had the curtain slightly open,but since we used the bed furthest away from the window it was of little benefit. It was only when I was getting my clothes from a chair by the window to get dressed that she came over to me to talk that I was able to appreciate just how attractive she was and what a great body she had. I plan on seeing her again  and I'll see if she might provide a better lit atmosphere. Also a while back I requested some natural light with the assistant of another provider prior to my appointment and she accused me of wanting to check for STD's.She also said "It would be like fucking in a parking lot at high noon " .I explained my vision issue and she eventually acquiesced.

I definitely can relate.  I once popped ON the room lights and she was pissed (like really).  I took a good look and shut it off.  Maybe better with the lights off.  HA!