Striving and action drive the plot of Goethe's Faust, making the re-translation absolutely appropriate for the character and the story. These values lie at the heart of Faust's character from the beginning of the narrative, when Faust sits in his study, ruminating over the mysteries of the universe. Despite all his scholarly knowledge, he feels that the inner workings of nature will forever be beyond his reach and, after the Earth Spirit he summons mocks his ignorance, he prepares to kill himself. Though he fears he has done all he can to advance his knowledge and understanding of the world, he is quickly dissuaded by the Easter morning bells – a reminder that this character is not one to give up actions so easily.
One way in which this theme of striving and struggling plays out in the narrative is through the struggle between opposites. From the deal between God and Mephistopheles (literally, "without light" – so the polar opposite of a God who is synonymous with light) to the earthly struggles between man and woman, opposite forces are constantly striving against one another in Faust. What makes Faust the ideal man, for Goethe, is that he continues to strive, despite everything. As God says in the Prologue, "For while man strives he errs." Goethe, through the character of God, believes that it is not the constantly good and righteous man who should be held up as the ideal, but the one who is constantly working towards something greater, even though his striving will inevitably lead to mistakes. Addressing the "why" of your question, then, one could say these are central values for Faust because they are character traits that Goethe wishes to promote as central to the ideal man.
At the end of the Prologue, we get more of an understanding of Faust's, and by extension, mankind's, need for action. God claims that "the Devil makes them do it"; literally, that is the Devil's purpose, according to God:
"I have never hated the likes of you.
Of all the spirits of denial
The joker is the last that I eschew.
Man finds relaxation too attractive—
Too fond too soon of unconditional rest;
Which is why I am pleased to give him a companion
Who lures and thrusts and must, as devil, be active."
The Devil is not an evil demon to be feared, but a necessary piece of the universe. Both opposites are needed: God to show the right path and the Devil to incite humanity to push boundaries. Again, the idea of activity for the sake of struggle is celebrated here. This God doesn't want blind obedience from humanity. He wants them to struggle and strive for something greater.
In Part One of the narrative, Faust's striving has a particular aim: to seek fulfillment through his own personal gratifications. Here we see Faust's actions taking a decidedly unrighteous turn. Following the logic of God, however, Faust remains good at heart, knowing right from wrong even as he engages in terrible deeds that result in several deaths and plenty of torment.
In Part Two of the narrative, Faust's actions have a different focus. Chastened (one would hope) by the consequences of his actions in Part One, he now strives to gain gratification through altruism towards humankind. Though his union with Helen of Troy ends in tragedy, he continues to strive for a moment of perfect satisfaction. Expanding his altruism to the poor, Faust plans a public housing project by reclaiming land from the sea. Faust declares his moment of perfection the one when he hears digging that he assumes is the beginning of his project.
The fact that his moment of perfection is one of perfect altruism, with no particular benefit to himself, shows he is fit for heaven. Thus, Faust's striving for knowledge and a moment of perfection is mirrored through the story with his own inner struggle between selfish evil and selfless good. Though both exist in humankind, it is the struggle that is critical. Any human striving for goodness is, inherently, good.