Leading up to the DLC for The Legend Of Zelda: Breath Of The Wild, some interesting discussions are coming up from Nintendo. Korok Seeds are the first topic of a series of blogs from Nintendo, this particular entry written by the game's director Hidemaro Fujibayashi. In it, he discusses how the Korok Seeds came to be and how they morphed from an entirely different mechanic.
It was also revealed that wearing the Korok Mask will give you the ability to find many of those pesky 900 seeds laying about as they'll rustle or make noise when you're nearby. A handy tool for when you're in need of dining more seeds to get gear slots. Below is a quick quote from Fujibayashi about the seeds themselves.
"There are many suspicious locations in this vast world of Hyrule. So during development, we started saying things like, 'It would be fun to discover something if it were placed at a location like this, don't you think?' Initially, we placed some random rocks in spots like these, just as an experiment. But as development continued, we concluded that simply placing rocks somewhere isn't intriguing or challenging enough to be rewarding, even if you were to find them. Instead, we suggested hiding some small creatures there for the finding. So that's how these Koroks, who would normally only live in Korok Forest, ended up scattered across remote areas of Hyrule."