The whole problem is the way they use meme burger and fries units to measure height and weight, so they don't have the intuitive correlation to healthy ratios between them.
Allow me to elaborate:
Since I use metric, I measure my height in meters/centimeters, in my case it's 1.75m or 175cm.
It's as simple as applying the common wisdom that my weight in kilograms should not exceed the number of centimeters above the meter in height.
This means that for a male height of 1.75m, 75kg should be my max weight, more than that equals overweight, for women you just reduce this by 10kg, so a woman my height should weight no more than 65kg.
This is taught basically everywhere from a very early age, everyone knows how the ratio works, so they immediately understand whether one is overweight or not, it's an internalized, automatic thing.

Now consider the equivalent situation in America, my height would be something like 5 big macs with 9 sets of medium fries with extra dip, one with cheese, and my weight would be around 160 large sodas.
Naturally, these units mean fuckall in an terms of understanding any sort of ratio or pattern to them, so why would I worry if my weight is 100, 160, 300 or 500 large sodas? Sodas are tasty, Isn't having more sodas better?