Interestingly this is a question I've had for a while. Night brings potentially deadly cold, predators, a drastic limit in vision so why do we find the sunset and night sky beautiful. Why do we stop and watch the sun set - something that happens every day - rather than prepare for the food and warmth we need to survive the night?
Maybe it's that we only pause to observe them and realize they're beautiful, when we're feeling safe enough?
"Beautiful sunset" evokes being on a calm sea shore with a loved one, feeling safe. It does not evoke being on a farm and looking up while doing chores and wishing they'd be over already. It does not evoke being stranded on an island, half-starved to death.
We think it's beautiful because it's like a background that we don't have to think about. If that background were hostile, we'd have to think and we would not think it looks beautiful.
You're entering the domain of philosophy. There's a concept of "the sublime" that's been richly explored in literature. If you find the subject interesting, I'd recommend you starting with Immanuel Kant.
My guess is that your framing presumes the opposite of the evolutionary reality. I think this time of day probably wasn't a big risk for us, that we were often the hunters and not just the hunted, and that the sense of beauty comes from — as the previous poster suggests — us having evolved to find it so.
That said, I'm discovering from living very close to a lake for the last year that mosquitos are a right pain around sunset…
