My general reading on that sort of thing is that while that kind of spell probably isn't too hard to learn (doing it right may be another question), it's more a question of 'is it worth it'. Like, when you can learn how to shoot a fireball at an enemy (which is clearly pretty bread-and-butter magic), how much time are you reasonably going to spend learning and mastering the ability to magically hide snacks on your person? To say nothing of how worthwhile it is or isn't to write that down and document it.

But, that said, it's clearly at least modestly available and has its uses. I'd say that a fair amount of Ninja techniques especially amount to finding useful purpose for what a lay person would dismiss as 'parlor tricks'. Karasu would not function as a character if he weren't able to pull that stuff off.