Every food commercial, advertisement, and packaging in the US is currently protein obsessed. I just bought 3 burritos, and the most noticeable thing on the entire package is its protein content. TV commercials about waffles are advertising that they have X amount of protein per serving. The products in my jobsite's vending machine have protein all over every package.
If you want to be muscular, then you need to eat a lot of protein.
If you want to be muscular and have a low body fat percentage, then you need to eat a lot of protein, and eat a lot of protein / calorie you eat.
If you're old and want to slow down how quickly your muscles waste away to maintain your physical health, you need to eat a lot of protein.
And protein is generally one of the more expensive parts of food, so companies constantly try and cut back and replace it with carbs and sugar instead... All leading to people seeking out food with high protein content