It isn't about "strong enough" because no one can define it. Strong enough to withstand a drop from waist level? Drop on staircase and tumble down? To soft or hard surface? Can you control the angle of the fall? These are variables where no one knows, that's why it's called "accidental drop". If someone bought an iPhone which by today's phone standard is pricey, why would someone NOT buy an SP? They are thin and barely noticeable.

The cost of an SP is negligible relative to the cost of replacing a screen in the event of unwanted incident.