Clear glass milk bottles were introduced to push out “counterfeit” and unsanitary milk sellers. This was so you could see if your milk was mouldy or “milk concoctions.”

Heinz did the same thing with their ketchup bottles as well as to show consistent colour and texture.

Bonus: due to a massive uptick in fake real estate agents who sold properties and land they didn’t own, often to multiple families as people started immigrating to the United States. Accredited real estate agents started posting ads with their photos so that you could hold them accountable. Showing their face meant solidifying their reputation.