You submit it to TASVideos. And there's lots of reasons. Challenge yourself. Discover new tech. Gain a greater understanding of the game. Create the perfect run. Compare tricks/routes and determine what's faster.

TAS runs are really fun to watch. Perfect play is very entertaining. Also, a lot of new tricks are discovered by the TAS community. Also, TAS runs have their own website.

ohhh okay thank you

This video explains why: