You really don't seem to remember or have been alive before a lot of these regulations were put into effect. Ever look at a food nutrition label? That one was fought tooth and nail.
It's been really interesting to watch the fight over GMO labeling. A lot of people who I'd normally consider to be on "my side" in this (pro-GMO) are strongly against labeling requirements.
Then there's the problem of the commercial code. If you say it's GMO, so that you don't get sued by GMO paranoids, then you could be sued by sane people for selling goods of a different description than the one on the label (by just saying it's GMO to be safe).
[0] https://en.wikipedia.org/wiki/Glyphosate
But i was mistaken on pesticides, the GM for plants to create Bacillus thuringiensis bacteria leads to a reduction in the requirement of pesticide.
EDIT: but this is not about what two HN commenters believe to be right or wrong, it's about the ability for consumers to discern for themselves what is right or wrong.
Because medically, that's a complicated question.
The 25-40mg/day number that's often cited is for added sugar, not inclusive of all sugar in food. That's something that's a little trickier to evaluate for processed food[0], and it varies a lot more between people than other substances for which a recommended daily value is listed.
[0] For example, fruit juice can have no sugar added, but still contain what are likely unhealthy levels of sugar depending on the serving size
That fine, but with all the misdirection around sat/trans fats, and the current global obesity epidemic, I find it hard to believe the industry is solely concerned about reducing consumer confusion (IIRC, that's their stated reasoning) around a % DV for sugar.
That is, we need some kind of yard stick for sugar, because what we have now is not sufficient for the problems our society has. It may not be % DV, but off the top of my head, say relative sugar ratio to other food products in the same category. But that can be gamed as well since there're only a handful of independent companies in the industry.
Right now, there isn't sufficient medical consensus to require labeling. A metric that is trivial to game can be far worse than not having one at all, as is picking a metric that ultimately turns out to be incorrect and counterproductive.
We know that, broadly, "too much added sugar isn't good". But we don't know exactly how much, or what the tradeoffs are with "replacing" added sugar with natural sugar (by substituting foods in diets), or with replacing added sugar with various sugar substitutes, or even if there is a meaningful difference between the different kinds of sugar (sucrose, glucose, fructose, etc.). There are speculations with some evidence to suggest reasonable hypotheses, but prematurely acting on those hypotheses has very far-reaching consequences.