I think it’s really brilliant marketing. If it didn’t say shatterproof, I never would have contemplated how shatterable my ruler is. Ruler durability was never even on my radar.
Since it did, I broke mine on the first day of first grade while testing it, and I needed a replacement.
When I was in school I went through so many of those cheap rulers because I’d leave them in my backpack until needed and theyd get bent through the forces of a child running around school with an overstuffed backpack of crap. So eventually my parents spent a few dollars on a flexible ruler which lasted multiple school years instead