For me it's about light and noise. Even if you draw the blinds in my flat you still get light through the window and no, I'm not going to be able to get blackout blinds in a rented property.
Too much light really stresses me out, I have long suspected I have SSAD. I don't mind it during the day, obviously, but when it's still light beyond, say, 9pm, I feel exposed and trapped. There's nowhere to escape to and you just have to wait it out. I'm on the road to getting therapy for it, or a diagnosis, because I don't want to live the rest of my life like this or making excuses and lying to people about how much I love light evenings when I don't. What makes it harder is that people just don't get it - you explain it to them and they laugh or think it's weird - so you just have to say nothing and smile and nod.
EDIT: posts like this just prove my point
https://www.easyblindsonline.co.uk/index.php?_route_=blackout-blinds/easynight-blackout-blind