In my mind, the two most possible options as to what they are come down to one question. (Of course, there are many other opinions and I'm not trying to offend anyone who doesn't think one of these).
Is turning into a Stalfos some property of the Lost Woods or something about being lost and wandering on forever without knowing where you're going?
If you think that it's a property of the Lost Woods, then it would makes sense that Hylian children that get lost in the Lost Woods turn into Stalchildren, since the adults turn into Stalfos. They wandered until they were only skeletons before finding their way back to Hyrule Field, where they stayed because that is their home. They might attack Link because they are angry with him for not helping them or saving them (when he is an adult, he has the Triforce of Courage, which is why they don't attack him then).
Then you could think that it is a property of being lost. This is my opinion. If Hylians are lost in the lost woods, wouldn't it make sense that Kokiri are lost in Hyrule Field? When they are at Lon Lon Ranch, they don't look lost in any sense of the word. They were introduced to the rest of Hyrule by the other races and welcomed there, as opposed to being lost, alone, and desperately trying to find the way back to their sanctuary. Also, it may have to do with the fact that Saria has joined the other sages and the rest of Hyrule, and so saved the Kokiri from being lost in all other places, but I think this last idea is pretty far-fetched.