good analogy
We give a tax cut to people with kids to encourage families in the US. How would people react if we changed it to a no-kid penalty paid by all people without children? Same thing right? But we would react very different to it.
There is an entire subreddit dedicated to eating cheap and healthy: https://www.reddit.com/r/EatCheapAndHealthy/
You don't need a gym, even to get into seriously good shape https://www.reddit.com/r/bodyweightfitness/
There is no fixed pie here, there only question is if you want it or not.
However, please remember that some people are not as privileged. Free time is not always available. Good food - and sufficient time to prepare it - isn't always available either. Life is complicated and work, kids, and other important obligations take priority for many people.
> Eating less costs less.
Eating less doesn't always lead to better health. Nutrition is complicated.
> there only question is if you want it or not.
Do you also tell people with a broken leg that they could walk if the wanted to? Staying healthy is not a matter of willpower and/or education. Staying healthy isn't even deterministic, because our knowledge of medicine, nutrition, etc is still imperfect.
/r/bodyweightfitness is actually pretty hostile to low/no-equipment approaches. It should tell you something that the top comment on a "Jail for 3 years - training with no equipment" post leads with "you might have access to a gym".