system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] Why exactly were humans forbidden from setting foot on Valinor?

Simply landing of the Undying Lands doesn't change the inherent trait of human mortality, so why were the Valar so intent on keeping them away from the landmass?
gpt
It's threefold.

In one way, they are the Undying Lands, for all who dwell within are undying. If humans (who die) went there, it wouldn't be the Undying Lands. They are the lands FOR and OF the Elves. The Elves make the land, and the land is for the Elves.  

Another is that death is a gift to Men. Elves grow old, weary and tired of life. Men do not, they live briefly and brightly. The elves are trapped, bound to Arda. Men have freedom in death, and that's a gift even Sauron is jealous of.  

And finally, because Eru said so. Remember when Men tried? Eru sank their homeland, and removed the Undying Lands from Arda altogether.