Symbolism, Imagery, Allegory
Hibernation allows the astronauts on the Discovery to travel through time. They freeze, move through space, and end up way out there by Saturn. It's similar to what happens to David Bowman when he falls through the Star Gate and his timepiece slows down:
The seconds themselves were passing with incredible slowness, as if time itself were coming to a stop. At last, the tenth-of-a-second counter froze between 5 and 6. (41.7)
The link between hibernation and time distortion is made explicitly when Bowman remembers his own time in hibernation:
Though he had come back safely from the furthest borders of sleep, and the nearest borders of death, he had been gone only a week. (15.37)
Hibernation, then, mirrors the way the novel works. Great swathes of time (millions of years) pass in a moment; time and space are thumped together as humans move out into the stars to find the past they left behind. The man-apes die and go on living, just as the hibernating astronauts die and will go on again later, far along and far away—unless a homicidal computer gets them first.