Can I just put this as an aside:
WHY does everything ALWAYS have to justify its existence with you people?! Justify this class, justify this race... Why can't something just be cool and fun mechanics with a nice name on top and a little fluff?! Why is everything always this whole song and dance?! It gets exhausting!
I'm not very fond of the "you people" here, but perhaps I can explain how many that feel that options should have justifications feel.
To put it bluntly (and fairly extremely):
If a race/class/whatever-part-of-D&D doesn't justify it's existence, it may as well not exist. If a race acts like a human (diet, culture, language, etc) and looks like a human (more or less), it may as well just be a human. It doesn't matter if they have rainbow hair, green skin, or are covered head-to-toe in shaggy hair, they may as well just be a human. Sure, real world humans can't naturally have rainbow hair or green skin, but that doesn't matter in a fantasy world, where literally anything is possible.
However, if there is something else to further differentiate the races - maybe the rainbow-haired race is actually a subrace of Aasimar that are descended from Unicorns, or the green-skinned race are actually photosynthetic and have a bond with nature (probably being dryads), and the overly-hairy people are actually Bugbears - then that helps "justify" their existence.
Sure, this isn't needed. It's a perfectly fine and valid way of playing D&D by having 70 different races for humans that act like humans and look like humans in everything but minor cosmetic differences (unnatural skin/hair/eye color, hair on unnatural parts of the body, language, minor mechanical differences (like size), etc), but that's not what many people prefer in their games. I like my world-building and homebrewing to be more in-depth than "another human race, but with purple skin" or "a homebrew class with innate arcane magic (like the Sorcerer),
but it's a Half-Caster". I'd be fine with an Arcane-Half-Caster similar in theme to the Sorcerer, or a race of people that look like Humans but with Purple Skin, but there has to be more to them than just those minor differences (Felshen in my world often have vibrant purple skin and other multicolored skin tones, like cyan, cream-orange, turquoise, and so on, and their psionic nature sets them apart from just being "multicolored humans").
The same also applies to creating new animal races. If Lizardfolk already exist, I don't need Crocodilefolk (Lizardfolk mechanics already work perfectly for crocodile people), Dinosaur-People, or Tuatarafolk. If Grung are playable, I don't need playable Grippli, Bullywugs, or Toadfolk (okay, I will admit that having one broader frog/toad-folk race with subraces for Poisonous Frogs, Toadfolk, and Wolverine=frogfolk would be cool). If Aarakocra are playable, I don't need different races for Hawkfolk, Eaglefolk, and Falconfolk. If Tabaxi and Leonin are playable, I don't need Jaguarfolk, Tigerfolk, and Ocelotfolk. (There are some animals that do deserve their own separate races, even though the concepts have some overlap, like Owlfolk and Aarakocra, Leonin and Tabaxi, Lizardfolk and Dragonborn, etc, but there is a line that has to be drawn to avoid crazy explosions of every different "animalfolk" variety of different types of birds, reptiles, and mammals.)
Anyway...
Elves and their relatives do not sleep. They trance. That means they probably don't have bedrooms and beds (trance chairs maybe?), and like the Minbari of Babylon 5, they probably see 'laying down' as a thing dead people do. They're probably creeped out by other folks sleeping and the concept of dreams must sound insane to them. They probably have a way different daily schedule compared to races that need lengthy sleep and coupled with darkvision might have activities that goes on 24/7 in different shifts. This also means you can walk into a Elven settlement at any time of the day or night and find random activities going on that you wouldn't associate with that specific time: day drinking revellers, kids playing in the street at night, classes etc. No proper bedroom and beds would probably also impact reproductive "activity" (Elven Kama Sutra?) compared to what we normally do.
This 24/7 culture, added to their long lives, might blend into a loose sense of scheduling where things happen when they need to happen, not because of a traditional schedule. They probably find the concept of specific meals for specific time of days to be quite funny. Pancakes were not invented by Elves. Add their mystical connection to nature and they probably always harvest at the perfect time without needing to really schedule it. I can see an Elf farmer getting up from a discussion at 1 AM and going "Well, time to harvest the apples!" simply because they 'heard' them be ready.
And I absolutely love stuff like this! It makes Elves seem unique and cool, and also helps inspire how to roleplay an elf (for both DMs and Players) differently from humans! The "I don't need to sleep, so my race is Diurnal" is an awesome hook for a reason to roleplay an elf! This is kind of thing is exactly what I'm asking to be more common in D&D races! This isn't even setting-specific, although it's specific to the elven race!
Dwarves have a low center of mass and they live underground, so they sleep standing up, Forest Gnomes are friends with nature fey and small animals that can alert them if enemies arrive, so they just take naps in the middle of the forest, curled up with a blanket of moss, and stuff like this creates a lot of really fun and interesting bits and pieces of the races that you can use to further differentiate one from another. Humans can't be as diurnal as elves. They (typically) can't sleep while standing up. They can't just face-plant out in the middle of a grove without fear of pests or predators disturbing them. These kind of things help give the races more unique identities, and are exactly the reason why I created this thread!
