G: Milk and cookies do complement each other in a few objective ways—but the pairing’s popularity, especially in the U.S., is also driven heavily by culture, nostalgia, and marketing.

Objectively complementary aspects:

1. Texture contrast: Cookies are dry or crumbly; milk is liquid and smooth. Dipping a cookie or drinking milk helps with mouthfeel and prevents dryness.
2. Flavor balance: Cookies are usually sweet and rich (buttery, chocolatey, etc.), while milk’s mildness and slight fat content can tone that down and “reset” your palate.
3. Chemical harmony: Milk contains fats and proteins (like casein) that can bind with compounds like tannins in chocolate, which reduces bitterness and enhances sweetness.

But:

• Not universal: If you didn’t grow up with it, it might feel weird or even gross (wet cookie, bland milk).
• Lactose tolerance: Large parts of the world have populations with higher lactose intolerance, so culturally, milk isn’t a go-to drink—making the pairing less accessible or appealing.
• Flavor preference: Some cookies (e.g., ginger snaps, biscotti) may be better with tea or coffee depending on what you like.

TL;DR:

There’s some objective synergy, especially with chocolate-based cookies and cold milk, but the strong emotional attachment in the U.S. exaggerates how "perfect" the combo is. It's tasty if you like both elements already.