This may be the best quote (from a linked article: http://www.bbc.com/news/health-27286872):

Prof Russell Foster, at the University of Oxford, said people were getting between one and two hours less sleep a night than 60 years ago.

He said: "We are the supremely arrogant species; we feel we can abandon four billion years of evolution and ignore the fact that we have evolved under a light-dark cycle.

"What we do as a species, perhaps uniquely, is override the clock. And long-term acting against the clock can lead to serious health problems."

That IS a good quote.

So it seems that the role of sleep is not just removing toxins but adding connections:

The mechanism by which a good night's sleep improves learning and memory has been discovered by scientists.

The team in China and the US used advanced microscopy to witness new connections between brain cells - synapses - forming during sleep.

Their study, published in the journal Science, showed even intense training could not make up for lost sleep.

Experts said it was an elegant and significant study, which uncovered the mechanisms of memory.

It is well known that sleep plays an important role in memory and learning. But what actually happens inside the brain has been a source of considerable debate.

...

A new reason for sleep was discovered last year when experiments showed the brain used sleep to wash away waste toxins built up during a hard day's thinking.

Sleep helps infants learn, too:

http://pandawhale.com/post/56893/how-to-help-infants-learn-and-remember