Item Recipes?

For an item like Magic Wand, I never see a recipe available for purchase in the Main, Side, or Secret shops. What happens is I can buy a Magic Stick and three Iron Branch and once I have all four items in my inventory they will auto combine into a Magic Wand for a cheaper price than buying the wand outright.

I'm confused because as I read some guides, there is early game discussion of picking up recipes and building towards them. It isn't a bad thing, just curious if I'm missing something.

Caveat: I've only done co-op bot games so far and have only been playing DoTA 2 for about a week and a half.

Not all items have recipes.

And picking up recipe as last item is the best because the recipe gives no bonus.