Social ranking, superiority and inferiority, domination and submission are common traits of human race. However, they do exist in animals and birds too. It is a common sight to see some dogs/wolves leading in a pack with others following meekly with their tails in-between their legs. It does make one wonder why do the meek animals accept the aggression so meekly.
It is simply an instinctive and evolutionary way of survival. The meek do so for their benefit. They know when they are in no position to go against the powerful, stronger and confident members of the group; the better option is to play along with the pack. They accept what they need to, for the sake of survival even if it means to be bullied and pushed around.
It isn't that they can't fight nor are cowards. They do have feelings and self-respect and the thought of being sub-ordinate doesn't appeal to them. However, they know that either they submit or get involved in violence and be killed. It doesn't make sense to go against the mighty, if you aren't ready. Hence, in reality the meek are simply waiting for their time; to come up to that position wherein they can challenge the dominating members.
If each were to fight, then packs shall not exist and the wolves/dogs shall not survive. Staying together in a pack is essential for their survival. Hence, the inferior ones accept the social ranking for peace and survival, and for their own benefits. Social ranking works for the meek. However, it doesn't mean that they are cowards or peaceful creatures. They are being wise and know that the time isn't ripe for them to rise against the mighty.
Hence, the meek coexists with the mighty in packs, forever alert to signs of aggressions or violence which they quickly diffuse and submit to the domineering demands so that they can stay on with the pack. They have the insight, strength, and capacity to neglect their own driving force to rise against the mighty. They shall rise only when the time is ripe and it is advantageous for them. Till then, they shall keep their heads down and put their tails in-between the legs. ? It is better to stay with the pack than starve.
Hence, you can see the power of the submission strategy as compared to aggression especially when it isn't in your benefits. They say either have the strength and courage to change what you can or have the serenity and wisdom to accept what you can't. This is exactly what the inferior wolves/dogs do. They have understood the means and rules of survival.
Moreover, it also explains why not all animals are pets? One prefers a dog to a raccoon, just because, dogs have mastered the art and skill of submission. They carefully nurtured and practiced it, and passed this on for generations.
Learn more of your dog forefathers from the Humane Society, or refer to books, articles and documentaries at libraries and/or internet.