What “real” food are you talking about? Be specific.
I just checked your profile and noticed you have a website.
The top article on it is Obesity and food palatability
Wow!!! From the guy who knows less about food and palatability than anyone on the planet. :eek:
The universe really does run on irony.
And fertilized by humans.
I lived, for a while, in an area where the staple diet was sweet potatoes. If you wanted to not starve to death, you ate sweet potatoes. Sweet potatoes was what there was to eat. There was also sweet potatoes. Rarely, they could eat pork, and I’m not sure when that was introduced. The only time I ever saw a bird, it was being chased by a man shooting arrows at it.
They also ate greens. If my diet was sweet potato, broken by occasional sweet potato, with sweet potato sometimes, I think I’d eat the greens sometimes too.
You’re still projecting your own assumptions about the available options onto earlier and vastly different societies.
If people had supermarket-sized levels of variety and quantity in food choices available to them at all times, would most of them choose low-sweetness vegetables over other kinds of foods for reasons other than their nutritional benefits? Probably not. (Indeed, we see from historical sources that typical diets in early industrialized societies tended to increase consumption of meats, sweets and starches (as well as tea, alcohol and other beverages not primarily consumed for nutrition) and decrease consumption of vegetables.)
But those are not the kinds of choices that our ancestors were dealing with.
You are also over-focused on a sort of TV-dinner mentality that assumes vegetables are intrinsically classified as separate “side dishes” to be served as accompaniments to, or less satisfactory substitutes for, the type of foods you consider “real”.
But that is not the default approach our ancestors took to vegetables.
Vegetables combined with other types of food can increase not only their nutritional value but their taste appeal.
I would not prefer Chinese beef-with-broccoli without the broccoli, or chef’s salad without the lettuce, or saag paneer without the spinach, or colcannon without the cabbage, or sausage-kale soup without the kale. Yes, if I had to make a choice between separate helpings of the green and non-green ingredients in each case I might go for the non-green ones, especially if I were food-insecure and consequently looking to maximize calorie and protein intake. But that doesn’t mean I would like the dish better without the green stuff.
But toast it and add butter and Marmite and he’ll give it a damn good try. 
My great-grandfather described his childhood diet as “potatoes for breakfast, potatoes for lunch, potatoes for dinner. On Sundays, Dad would have sausage with his potatoes.”
After that many potatoes, being able to have black beans with bacon, carrots and potatoes, or chickpeas with spinach… was Heaven on Earth.
Wanna come feed the Nephews? They drink their veggies, even though I swear those things are in solid form. I’ve tried listing the veggies we hated as kids vs the ones we ate without problem (despite Mom’s horrid overcooking of them), the first list is shorter despite allergies being involved.
You <> everybody.
Also, many of the weeds are vegetables in their own right - I can typically pick weeds for use as green vegetables quite a while before my own greens are ready for harvest. I can very easily imagine people eagerly looking forward to the first chickweed, nettles, wild garlic, goosefoot, cow parsley etc. of the spring.
After a long, dark winter of eating barley gruel with maybe a few pulses, a little dried fruit and occasional cured meat, anything fresh and different would be very welcome.
Well, you would say that, wouldn’t you. 
Don’t forget purslane and dandelion in that list, Mangetout. Both are delicious. At Easter dinner, given the first-world luxury of choice of foods, I’ll usually have a little sliver of ham, a half-serving of mashed potatoes, maybe a little of whatever the side dish is, and about four heaping bowls of dandelion salad.
Ah. English haut cuisine.
Indeed. There’s presumably a reason they call it “cow” parsley.
This idea of hating vegetables has always mystified me. I don’t like the texture of eggplant, and I can live without zucchini. Other than those, I’ve always liked a variety of vegetables. Perhaps this is because they weren’t boiled to goop in my childhood (though I don’t mind a lot of them served as vegetable mush, either).
I forgot to mention the other end of the year. Cabbage and cabbage related greens get sweeter after the frost hits. In fact you can allow a layer of snow to cover them and then just go dig them out all winter long. Can’t do that with grains or fruit.
For root vegetables, you have to dig them up before the ground gets too hard, but, like properly stored grain, they can last the winter, too. Whole wheat flour goes rancid quickly, and the miller takes a tenth of it to grind your wheat. Not to mention that travel to the mill and back might be difficult in winter.
Sometimes, you either eat the wheat boiled (frumenty), or you hand grind the flour. Once you start hand grinding, I think the effort for calories goes up a tad. And did you really take the effort of harvesting whole fields and winnowing into account. Plus the shooking and shoveling and storage and travel. For vegetables, you only grab what you need or what’s coming ripe a lot of the time.
Ah, yes. The time honored tradition of the slops garden. A slops garden is lettuce and other salady, quick growing stuff planted by the back door. Since we’re talking about a time before indoor plumbing, boys and men step out the back door and pee against the house wall. Makes the lettuce just spring up. All you have to do is reach out the door and grab some.
Oh, I hadn’t noticed that you said that the whole plant had to be picked. It doesn’t. Up through medieval times, cabbage and lettuce were not heading plants. They were loose leaved. Breeding for heads came later.
So you step out the back door, lean down, and pluck the outer leaves from the plants until you have enough. You leave at least half of the leaves still there. New leaves will grow up in the middle to replace the ones you took. Lettuce plants will keep producing new leaves until the days get short enough to signal the plants to bolt and set seed.
Continuous production. Plant a few rows, harvest all spring and summer.
Adding to the side dish comment, some folks only had one pot. Especially on days when everyone had to be out working, the pot would get filled with whatever was on hand - mostly grains and vegetables - and then put on the coals. It was a mush by the end of the day. But if you’re doing physical labor all day, with no lunch, you’ll get as much of that mush in you as you can.
Greens bolt in the summer, not when the days are short.
Here’s the traditional Spring dishof Northern England, made with various wild greens.
More to the point, HG lifestyles can only support relatively small populations.
Yes. Thanks for the correction. It’s been too long since I had a garden.
Also too long since I checked out the local planting chart. I’ve heard that California has a “Mediterranian Climate”, though, so we might not sync with the rest of the country.
Interesting to see how the lettuce is different from the spinach is different from the cabbage.
The OP seems to assume that they weren’t aware of vitamins but were aware of calories. That makes no sense. It’s more reasonable to assume that they weren’t aware of either of the two values of food. If we assume that, then it’s reasonable to assume that they considered any source of food to be “food” and full of energy and health. Hence, it’s no mystery that they ate whatever they could get.