system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do products in the USA say "made with real milk" or similar? What else would they use?

I got this question from a friend from Germany and as an American I...actually don't know, and googling is only showing milk advertisements, or ehy milk is a lie not why it says "Real Milk."

Edit: thank you for all the answers, the topic is covered!

Also, I saw many answers that are not talking as though you are speaking to a 5 year old, or some spiraled into why milk is a lie. Milk itself was not the topic of my question. :/
gpt
In the 1980's there was a trend for cheaper products to contain "cheese" that had no actual milk in it - it was basically a blend of hydrogenated vegetable oil that *sort of* mimicked the appearance and taste of cheese.  This became especially prevalent in cheap delivery and store bought pizzas.

People began to assume that all cheap pizza was made with fake cheese, so companies like Dominos and DiGiorno started sticking big "MADE WITH REAL CHEESE!" labels in their advertising and on their products.  A lot of local pizza chains also developed advertising materials based around the fact that they used real cheese - Round Table Pizza, which is a major chain in the western US, used the phrase "The Last Honest Pizza" for a long time to indicate that they used real cheese.

This became so widespread in the pizza industry that its now spread to other areas as well.  A lot of products advertise that they're made with real milk if for no other reason than that it looks weird for someone to see a row of products that all have that label on them and then one that doesn't.  Its sort of a weird labelling arms race - as products that are located nearby in a store begin using labels like that, other manufacturers start using the label as well so that their food isn't perceived as an inferior product.