As vegans, we should know better than anyone that protein deficiency is a myth. Has anyone come across anyone in their entire life that has been protein deficient?
Big difference between being "protein deficient" and not having adequate protein intake to reach one's training goals. They're two totally different beasts.
"Protein" foods are not specifically required.
Maybe not for mere existence, but again, the goals of some people may require additional protein intake. There's yet to be anyone I've ever seen who gained any significantly impressive amount of muscle mass on a low protein diet, the most I've seen are some guys who maybe gained 5-10 lbs. of lean mass and lost some bodyfat to show better definition, but never anyone who had the size to viably compete in bodybuilding or the strength to compete in any form of strength athletics. Maybe someone out there has managed, but if they have, they're keeping well hidden from the rest of the world
If you were to poll most of us here who have been aiming to get larger and stronger, you'd find that the bulk will all attest to better gains when taking in higher protein. I personally need moderate protein to see any significant gains in size or strength with my training (usually 150-180g/day), and higher than that (190-230g/day) if I want to lose fat without losing too much lean mass. Taking in high carbohydrates, even as raw fruits, only succeeds in destroying my goals for fat loss and is completely unsuitable for my body type (and likely that of quite a few others who tend to be carbohydrate-sensitive).
Most "protein" foods, milk, meat, nuts, and seeds, are all higher in fat and should be looked at as so. They tend to lead to an over consumption of calories and thereby inducing weight gain.
But, that fails to explain how some like myself gain fat on calorie-restricted diets high in carbohydrates (even fresh fruits being a primary source) and low in protein while I get the best fat loss with a lower carbohydrate / high fat high protein diet. I have taken the same caloric intake and done it with two different programs, one high carb and one low carb, and the low carb one is the only one that worked as the high carb "fat loss" approach only made me fatter by failing to reduce bodyfat, though it DID help me shed some muscle that I never intended to lose, the complete opposite of what I'd aimed for.
Not trying to get back into a big debate all over again, just saying that the proof of a low protein diet being remotely optimal for those whose goals are size/strength has never held water. For the average person who has little to no concern over anything but getting through their daily life without being involved in athletics, protein probably has little worry for anyone needing "extra". But, for strength athletes, low protein is the enemy of most. Trust me, I know plenty of guys who would LOVE to be able to save tons of $$$ by not stuffing themselves with tons protein to reach their goals, they just don't get much on their effort of hard training unless they keep the protein up. Hence my decision to always chime in when people decalre anything beyond minmal protein to be non-essential - maybe not for their
goals, but for others, it may be something that's necessary.