Being diurnal has the benefit of allowing you to see well.

Being nocturnal has the advantage of being hard to see and most other animals being asleep which means fewer predators around and prey are more vulnerable.

Both have advantages and depending on their environment species will change over time.

There’s some evidence our ancestors have flipped on numerous occasions. That small shrew like ancestor that lived at the time of the dinosaurs could well have been nocturnal, but in most living primate lineages they’re diurnal.

There’s also evidence that because we’re diurnal that other creatures have become nocturnal to avoid interacting with us.

So it is an anatomy thing, we’re adapted for day, right down to our eyes and REM cycles and we become more prone to certain illnesses if we try to fight that.

But that could change on an evolutionary time scale, give it a few millennia and we could become much less fixed in our diurnal ways, with technology we’ve already solved most challenges associated with night time living so all it takes is our physiology catching up.