Protein considerations are largely a myth. You'll get your proteins unless you go out of your way to avoid them, you don't need them in every meal unless you're a bodybuilder or something.
Protein needs are not a myth, and are backed by some of the most extensive research in the nutrition field. See for example examine.com: https://examine.com/guides/protein-intake. The recommended amounts are far higher than most people get.
As mentioned down-thread, gaining and maintaining muscle mass is not just for bodybuilders, it's incredibly important as we age to maintain quality of life. Sarcopenia as a result of disuse is one of the plagues of our modern times, and contributes to huge quality of life declines as we age.
You'll get your proteins without even trying, as long as you're eating a somewhat normal diet. Look at the table in your own link titled "Combining incomplete proteins". Just don't eat only the one thing all the time and you'll be fine.
I’m fairly active, and currently losing some weight, both of which raise my requirements, but it’s not like some sort of niche use case. I track what I eat using an app with a reliable macronutrient database, so the incidental protein is all accounted for. I can assure you that getting anywhere near the recommended amount doesn’t happen by accident, unless I massively blow my calorie budget.
"Cutting" isn't a normal diet. Weight lifters do track their macros more closely to make sure they're getting enough protein on a caloric deficit. It's very easy to starve yourself "the wrong way" while doing it. It's absolutely niche. Of 300 million Americans, during an obesity epidemic, how many do you think are cycling bulking and cutting?
It's ridiculously easy to get your recommended daily averages even as a vegetarian without thinking about it. Rice and beans? Complete amino acid profile. Same with bread and butter. But let's get into statistics and leave the anecdata behind us! Most Americans are consuming double their recommended protein intake, but half the fiber: https://www.deseret.com/2024/1/30/24055585/americans-eating-...
It's not surprising that that article thinks that people are getting twice their daily requirements, if it claims that men need 56g/day. Really? A 50kg man and a 120kg man have the same protein requirements?
Aside from that, there is plenty of evidence that the RDA is woefully insufficient, e.g.:
That second article says in its summary: "Current evidence indicates intakes in the range of at least 1.2 to 1.6 g/(kg·day) of high-quality protein is a more ideal target for achieving optimal health outcomes in adults". That's slightly lower than Examine's figure of 1.2 to 1.6, but whatever. Even assuming the lower figure of 1.2, 56g would be sufficient for a 46.7kg man. I don't know many of them.
That's just after a 30 second search. I can't find the study right now, but if you lock people in a metabolic ward and only give them the RDA of protein, they lose muscle mass. It's not even sufficient for maintenance.
I'm not a bodybuilder, and I'm not "cutting", I'm just losing some weight and want to make sure that what I lose is fat, not muscle. Again, maintaining muscle is about much more than bodybuilding, maintaining basic strength is essential to living a pain- and restriction-free life. I'm more systematic than most because I know that makes it more effective, but wanting to lose weight is not a niche use case. I'm also trying to get my parents to eat more protein because they're older and there's plenty of evidence that their needs are higher, and it's very difficult for them as vegetarians (partly because they resist lifestyle change, admittedly).
If you don't have a habit of eating meat every day, it's pretty easy to eat a low protein diet. So you have to try and keep track of it, especially if you are vegetarian and even more so if you are vegan.
Or unless you care about maintaining muscle mass, which should be either #1 or #2 on your list if you care about lifespan and healthspan (the other one being cardiovascular fitness).
Basically the problem with focusing on protein is people will tend to eat more meat, which has terrible cardiovascular consequences, rather than what they should be doing which is varying their nutrition, not analyzing a single food for its protein content. Don't eat just the one food, people.
Different organisms have different metabolic pathways. Humans are unable to synthesize 9 of the 21 most common amino acids, and must acquire them from food. To learn more, look up "Essential Amino Acid".
Cows do it by having a complicated multiple-chambered stomach full of specialized bacteria that can digest cellulose -- basically a natural chemical engineering facility.
