The Legend of Zelda: Tears of the Kingdom reveals a good deal of story through memories, similar to its predecessor, Breath of the Wild - this time memories come to Link in the form of pooled Dragon Tears. Just like in BOTW, collecting memories in TOTK isn't strictly necessary, even though they constitute a main quest. However, players might find that hunting down the Geoglyphs to get every Dragon Tear is worth the effort.
[Warning: The following article contains spoilers for The Legend of Zelda: Tears of the Kingdom.]
Breath of the Wild starts with Link waking up without his memories, and players can collect those memories to fill in the events of a hundred years ago. While Link hasn't lost his memories again in Tears of the Kingdom, the Dragon Tear memories help to fill in parts of the past. However, the focus isn't Link's past: it's the past of Hyrule and the story of how Ganondorf came to be sealed with Rauru's arm.
You Should Find All The Dragon Tear Memories In Zelda: TOTK
Of the 18 memories players can find in TOTK, 12 of them are from Dragon Tears. Beating Tears of the Kingdom might not require finding each Dragon Tear, and doing so can be time-consuming, but the memories from them add a lot of context to the story, particularly regarding what happened to Zelda in TOTK. Completing the temples and awakening the sages help to explain Ganondorf's evil deeds in the past, but how he gained his power is further explained through Dragon Tears.
The History Of Hyrule In Zelda: TOTK
Ganondorf isn't the only character players learn about through memories in TOTK. They also show Zelda's journey in the past since she ended up in the era of Hyrule's founding. And because she's so far back in time, she meets her ancestors - the origins of the powers she inherited - and learns a way to repair the Master Sword for Link. As an extra incentive, collecting every Dragon Tear leads to another Tear falling from the Light Dragon, and this one explains whose memories players have been witnessing.
Open-world games have a tendency to hide lore, and one way TOTK does this is through Dragon Tears. It isn't required to collect these memories, but it makes sense that they're listed as a main quest if players do speak with Impa to begin it due to the amount of information relevant to the game's story the memories give. For players who want to learn more about this version of Hyrule, its royal family, the Zonai, and Ganondorf, they'll want to find Impa and search the regions for Geoglyphs in The Legend of Zelda: Tears of the Kingdom.
Source: Nintendo of America/YouTube