SureAI

You can find books that gives you skill points and memory points, but nothing that gives crafting points.
Is that by design or did I miss it?

Design. But You can submit a suggestion at the bug tracker.

Are you referring to the rare books that give you something like +2 LP or +2 memory points? If so I don't recall any giving "+" crafting points. EDIT: I just checked the "Loot Guide" appearing elsewhere in this forum, and it shows a Learning Book +1 MP and another +2 LP, but no "+" crafting one.

Why is just crafting points limited?

Well, perhaps because there are 12 "combat" skills but only 6 crafting skills. It could be a matter of balance. If you got lots of crafting points early on, you could make some weapons that were quite a bit stronger than what you might find, when you have weak enemies to face.