When we buy something, we generally just expect the product's label to tell us how to use it. And if there are special warnings we need to know about, those should definitely appear there as well.
But sometimes, a product is straightforward enough that's legitimately hard to think of what you're supposed to say on it. And for some companies, that empty label space is a chance to get creative.
Naturally, you'll get some fun results if you turn somebody lose with a label maker, but even those who have to worry about manufacturing costs like to have that kind of fun, too.