[simplify]

> If they did, what's stopping everyone else from doing it? I am expressing doubt.

This is a pretty interesting topic on human nature. Chain of reasoning doesn't always result in proper action. For example, my cousin has been having a lot of health problems lately. Logically he knows that alcohol is contributing to them. Yet, when he's out with his friends, he can't help but drink anyway, despite knowing (and likely ignoring for the moment) the consequences of doing so.

Similarly, things like junk food and overpriced status-symbol vehicles have objective costs that prey on the weaknesses of human nature. Whether to restrict such things, and by how much, is where the subjective aspect comes in.

This also all presumes we share the same values of "let's try to reduce human suffering somewhat". A libertarian, for example, would just say "live and let live".

[rtpg]

Right, totally see what you're saying. In the junk food example (assuming fast food a la McDs...) it feels fairly noncontroversial to say there's health costs. Just then you get into convenience discussions (or even just enjoyment discussions) and now you're weighing health vs convenience and these are totally not fungible quantities. So you're already veering into subjectivity if you're saying "on balance it's bad".

There has to be a point at which you pull in preferences. But at least then you can split the "objective" from the subjective, and think about the details in earnest. Even when conclusions differ.