Why no labels? This is an issue that comes up again and again, and there are plenty of good reasons:
1) You irrationally single out a single aspect of crop improvement. Where are the labels for hybrids, open pollinated lines, crops developed with mutagenesis, crops developed with induced polyploidy, bud sports, crops produced with somaclonal variation, crops produced via embryo rescue or with wide crossing in their lineage, ect.? We don't label them. We don't label them because corn produced via a doubled haploid hybrid is still corn, an apple that is a bud sport is still an apple, and a zucchini that is genetically engineered is still a zucchini.
2) You tell the consumer nothing. I modified my computer; tell me what I did to it. If I say that a crop is genetically engineered, tell me what that means. Tell me what I did, why, what it means, what are the benefits. Is it insect resistant, herbicide tolerant (if so which one), virus resistant (if so which ones), drought tolerant, how do those genes work, why are they used, what are the benefits? Unless you already know what is what (see point 4), saying that something is GMO doesn't actually tell me anything, does it?
3) You do not correct any misinformation. People are afraid of GMOs. Unfortunate, not scientifically justified, but true. Non-GMO labels are everywhere, even on crops where there are no GMO varieties, as a marketing tool. I saw non-GMO labeled figs and non-GMO labeled basil the other day..there is no GMO figs or basil on the market, anywhere. Remember that old XKCD comic about marketing? Make no mistake, this is both marketing for the companies that convenient sell non-GMO crops, as well as ideology. Professional activists at Greenpeace and the Center for Food safety have made a career of denying science and spreading fear. A label does nothing to correct that and can very easily be taken as a sign there is something wrong with the food, when there really is nothing.
4) You can already tell what crops are and are not genetically engineered. Corn, soy, canola, cotton, alfalfa, sugar beet, summer squash, papaya. Learn about them, and you can know. Too hard for you? Too damned bad, this is your ritualistic impurity beliefs, you take responsibility for it. Just like Kosher or Halal, you can avoid what you find questionable, or buy specially labeled things.
So, you want to select one thing, tell nothing about it, and correct no deficiencies in public knowledge? That's not informing people, that's a lie of omission. It is no different from the 'Evolution is just a theory' labels. Yeah, it was technically true, but taken so far out of context that it was deceptive and everyone knows it. This labeling nonsense is politically motivated crap and everyone knows it.