Why has nothing evolved to not need sleep?

[Beerina]

Actually sleeping is an evolutionary advantage.
It helps conserve energy and sleep is believed to aid in processing memory.

Ding, FTW!

Sleep evolved. Bacteria don't sleep, AFAIK. Animals sleep because it was to their advantage to rest, i.e. not consume as much energy, and so on, and it just got incrementally better from there on.

 

[Perpetual Student]

Energy conservation certainly appears to be a good candidate for a selection advantage for sleep. If this has already been said, sorry for the redundancy: Darkness is dangerous. We can fall off an unseen cliff, fall into a body of water, walk into the trap of a predator, or simply trip and break some bones. I have no doubt that being idle during darkness has a selection advantage.
The combination of the two (energy conservation and danger avoidance) provide a potent selection advantage for nighttime sleep.

 

[EHocking]

Energy conservation certainly appears to be a good candidate for a selection advantage for sleep. If this has already been said, sorry for the redundancy: Darkness is dangerous. We can fall off an unseen cliff, fall into a body of water, walk into the trap of a predator, or simply trip and break some bones. I have no doubt that being idle during darkness has a selection advantage.
The combination of the two (energy conservation and danger avoidance) provide a potent selection advantage for nighttime sleep.

OK, so this is only one example and not put forward to refute the energy conservation hypothesis, but this particular wader, when flying non-stop while migrating, alternately shuts down (apparently) each side of it's brain while flying. (oh, just like the dolphins/whales mentioned before).

So is this mere energy conservation, or is there a neurological requirement for resting the brain?

 

[Ordover]

Do to the nature of their biology, some cold-blooded animals go dormant at night, including the ancestors of mammals. Since they were dormant anyway, evolution made use of that time to do whatever "housekeeping" chores take place during sleep, since the animal was not going to be "on" anyway. Those housekeeping chores are clearly somehow vital to survival and couldn't be dropped or spread out, so we have the period of dormancy continuing to show up in mammals like us.

Different animals have different sleeping patterns. Some cats sleep as much as 16 hours a day, and their waking hours are split between day and night since they funcation equally well in both. The long sleep between periods of high activity keeps their metabolic requirements lower, which may be an advantage, especially if food becomes scarce.