Who is the servant in a family? The parents are servants. They provide everything for their children, and do everything for their children. Why? Because they can. Their children are weak and they are strong, so the stronger does the work that the weaker is in need of. Parents do this because they love their children. When you love someone, you want to do any good for them that you can.
In the rest of the world, things are different. The greater person is served by the lesser. This is because the greater person has the capacity to force the lesser to serve them, whether by actual force or by withholding money until the work is done. People do this because they do not love each other. When you do not love someone, you look at them and wonder how you can use them.
Jesus is telling us that the world should be more like a family. The greatest person is the servant in the Kingdom of Heaven. Jesus did for us what we could not do for ourselves. In return, we can do nothing for him, because he needs nothing from us. Instead, he tells us to look to the weak of this world and serve them. Find someone whom you can help, who is unable to do something for themselves, and take care of them. In other words, pay it forward. That is what Jesus means when he says, “Love one another as I have loved you.”
Of course this is all just more logical. Why would the weak serve the strong? That is foolishness, but it is the way of the world. If the world is a pyramid, the strongest ought to be on the bottom holding up the weak. At the very top should be the weakest person in the whole world, the person who cannot do anything for themselves or for anyone else. The world says that we should kill that person. Jesus says that we should serve them.
This is why the angels serve us; they are stronger than us. Who is considered greater: the President of the United States or Blessed Theresa of Calcutta? We forget presidents. Who remembers Chester Arthur? We remember saints. The scribes and the Pharisees sought human approval by trying to put themselves above others, which only makes others mad and/or jealous. We have put ourselves below others, as their servants, if we really want approval.