Not every product is used exactly the way it was intended, and many familiar devices have primary uses we've never heard of. For example, many people don't know that the backside of a hammer is meant to remove nails, or that you need way less laundry detergent than you think. But some manufacturers know that customers are misusing their products, and choose to continue making them the same way anyhow.

For example, bobby pins are actually meant to be worn with the ridged side facing down instead of up. That goes against the conventional wisdom, and what most people would consider more aesthetically pleasing. The pins could very easily advertise their correct and much more functional usage, but they essentially have their niche covered, and doing so doesn't seem like it would impact sales. Bobby pins don't care if you use them wrong, and they won't stop you. 

But pins are harmless. Lots of other products, especially medicines and kitchen devices, get used in drug production. Cough drops could make themselves less appealing for the drug community and better at stopping coughs, but then they'd lose money. And we'd all have way less fun. We'll all keep using things the way we want to, thank you very much.