The Legend of Zelda: Ocarina of Time first graced Nintendo 64s in 1998 and continues to hold a place in the hearts of many fans of the series. This game focuses on the story of a young boy named Link who lives in a place called Kokiri Forest. One day, a fairy named Navi is tasked by the guardian tree of the forest, the Deku Tree, to find Link and guide him on his journey to save Hyrule. From there the player, as Link, travels all around Hyrule to find items called Spiritual Stones, which are needed to open the Sacred Realm and find the Triforce before the evil Ganondorf. Eventually Link successfully collects the Spiritual Stones, but, when he uses them to open up the Temple of Time and attempts to remove the Master Sword, he gets sealed in the Sacred Realm for seven years. The game continues with the older version of Link, but how well does it answer the question of why he was sealed in the first place?
The best explanation for Link being sealed in the Sacred Realm is actually given by the Sage of Light, Rauru, when he first wakes Link. Rauru's explanation for Link's slumber is that the Master Sword is supposed to only be pulled out by the one worthy of the title "Hero of Time." Link might have been able to pull it out, but Rauru explains that he was too young to actually be the Hero of Time, so his spirit was sealed for seven years, only being released when he was old enough to be worthy. This seems like a pretty good explanation at surface level, but why did Link have to be sealed? Wouldn't it have been fine for him to exist in the world for those seven years, returning when he was able to be the Hero of Time?
The easiest explanation for Link's slumber is that it was the best way to fit the intentions of those designing the game. After all, it not only allows for an interesting game mechanic of playing with time, but it's also the perfect way to make the kingdom of Hyrule feel new again. This time skip is actually one of the things that makes Ocarina of Time such an amazing game, even today. Despite Link getting sealed for seven years being a great mechanic, could there be other reasons for sealing him? After all, Zelda was able to survive those seven years, so why wouldn't Link?
Zelda Survived Where Link Couldn't
In The Legend of Zelda: Ocarina of Time Link probably wouldn't have been able to live through the seven years he was sealed, were he actually allowed to leave the Sacred Realm. Even Zelda was only able to survive thanks to the support of powerful people like Impa and her disguise as Sheik. Ignoring the danger of Ganondorf himself, Link being worthy of the title "Hero of Time" means that he probably wouldn't be able to ignore the evil acts that Ganondorf was committing during this time. Can you imagine young Link trying to complete something like the Water Temple without be able to use items like the hookshot? It probably wouldn't be a pretty sight.
In essence, Link was sealed for seven years in The Legend of Zelda: Ocarina of Time for the exact reason that Rauru gives in the game. He wasn't ready to be the Hero of Time and without the power of tools he can only use when he's older, like the Master Sword, Link wouldn't have been able to do much about Ganondorf's plot anyways. Another point is that if Link hadn't been sealed, no matter how many heart pieces he collected, it's more than likely that he wouldn't have survived those seven years until he could wield the Master Sword. It might make the plot of The Legend of Zelda: Ocarina of Time seem even darker than it already is, but there likely wasn't another way to beat Ganondorf beyond Link getting sealed up for a while.