Because the individual and collective benefits are eternal.
"Ever since Eden there has been a deadly conflict between the followers of Christ and the followers of Satan. Not to know this is not to understand the most fundamental warfare that’s been going on since the dawn of human history." ~ Fr. John A. Hardon, S.J.
Fr. Hardon reminds us that Jesus began His public ministry by fasting for forty days in the desert. Then, He allowed Himself to be tempted by the evil spirit.
"...part of the imitation of Christ is to expect, and I mean expect, to be tempted by the devil. Indeed the greater and firmer our desire for holiness, the stronger will be the efforts of the fallen angels to make us follow their example of refusing to serve God." ~Fr. John A. Hardon, S.J.Have you noticed this occurring in your own life as you strive to grow in holiness?
Fr. Hardon tells us that it is vital to recognize the demons’ strategy, and "courageously act against what they are urging us to do."
They urge us to "self-indulgence, the key to Lucifer and the key to the demons’ temptations of us. The key is self, self-indulgence, self-assertion, self-will. The impulse leading to this self-will is from the minions of Lucifer, who became the devil precisely because he used his will... Once the free will turns against God it becomes demonic."
"The new pagan worships only one god, and that one god is man himself..This new paganism idolizes each person's own mind; it idolizes each person's own will...The god is no longer the infinite Creator of the human race, it is man himself." ~Servant of God, Fr. John A. Hardon, S.J., Neo-Paganism
"The essence of religion, on these terms, redefines the meaning of truth." ~ Servant of God, Fr. John A. Hardon, S.J., Neo-Paganism
Our obedience is vital so God can accomplish His plan of Salvation through us according to His most perfect will. Our adversary is cunning, and markets disobedience, arrogance, and selfishness to us as good things when in fact we should be aggressively striving to become more obedient to God, humble, and selfless. May we strive every single day, from moment to moment, to live, love, serve, and suffer in imitation of Christ.
The Sacraments are vital as we strive to accomplish the will of God and grow in holiness. Frequent participation in the Holy Sacrifice of the Mass, frequent reception of the Eucharist, and frequent Confession are necessary.
Why become holy? Growing in sanctity is God's will for each one of us. It is a vital part of every person's apostolate, or life purpose. As we grow in holiness, we become better at uniting our wills with God's will, and are unified with God. The holier we are, the more holy we want to become. In fact, we find ourselves asking God to transform ourselves into Him. Jesus, meek and humble of heart, make our hearts like unto Thine!
Our efforts to become holier not only benefit ourselves, they also benefit others.
What effect does my, or anyone's, sanctity have on others?
"...the following of Christ is a social enterprise. We must go beyond the desire for our own sanctification to cooperate with Christ in propagating His doctrine among all men throughout the world. Togetherness is of the essence of our faith." ~ Fr. John A. Hardon, S.J.
Our adversary does not want you to know this vital truth. Be sure you understand it and remind yourself often. Teach others, especially young people.
"...we are to be channels of grace to others. No one, and the word is no one, ever enters our lives, not even for a moment, except that God intends to be a channel of grace through us to that person. But we will be effective channels of grace to others and God will use us only in the measure that we possess God's grace ourselves. Only holy people sanctify other people. God will use us to sanctify every person who, even casually, even momentarily enters our lives, only the in measure that we ourselves are possessed of the grace of God." ~Fr. Hardon, S.J., A Day of Marian Reflection
"What this means to all of us who
wish to follow the Savior, and mind you not merely follow Him individually,
but follow Him as one who wants to brings others, through us, to follow Him.
We must look around or search for rejection or dishonor. Do we to have to look
around? No. They will come unbidden, unsolicited...the key element
here is the disposition of will, which is ready to endure. Let me go through
the litany, scorn or contempt even, in the faithful following of Christ, but
mind you, in the faithful following of Christ the Leader, the One who is inviting
the whole human race to follow Him. 
"The net result, on our part of sincere detachment
from creatures and corresponding attachment to Jesus Christ who Himself was
scorned and condemned, is deep, deep, deep humility. And a perfect synonym for
this deep humility is interior humility, inside humility, in the mind and will. "Humble people and only humble people are used by Christ to propagate His message of salvation to the world. Let me repeat. Only humble people are used by Jesus Christ to propagate His message of salvation to the world. And Christ knows who is humble and who isn’t.
"But don’t you dare for a moment suspect that humble
people are, well, stupid people or that humble people are weak people. Oh, no.
Humble people can be extraordinarily gifted people. Ah, and the more gifted
they are, the more God will use them. Provided, that’s the proviso, provided
they are really, sincerely, profoundly, interiorly humble." ~ Servant of God, Fr. John A. Hardon, S.J.
Looking for more exceptional material on this subject, consider The Two Standards: Christ and Satan, from The Spiritual Exercises of St. Ignatius Conference by Fr. John A. Hardon, S.J.:
http://www.therealpresence.org/archives/Christian_Morality/Christian_Morality_003.htm
"Never run away from the Cross. Never." ~ Fr. John A. Hardon, S.J.
God is at work in you!
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Sources:
Fr. John A. Hardon, S.J. Archives, The Two Standards: Christ and Satan, from The Spiritual Exercises of St. Ignatius Conference by Servant of God, Fr. John A. Hardon, S.J. (Inter Mirifica, Copyright © 1998).