It's a great question.  And there's a great answer.   Baptism removes Original Sin, but Jesus never sinned and was born of a woman who was preserved from Original Sin (and so could not be passed on to her progeny, Jesus).  So it might seem pointless for Jesus to receive baptism.   

But the baptisms by John in the Jordan River were not sacraments.  They were sacramentals.  In other words, they did not convey grace, but served as a physical marker for those among the Jewish people who were committing to reform their lives away from sin, in response to the Baptist's message.  

Jesus, however, wanted to be baptized -- not because He needed any kind of grace -- but because He wanted to transform John's sacramental into a life-giving sacrament.  

Jesus, in submerging himself in the Jordan, accomplished two things:

1) He sanctified the waters of the Jordan for the purpose of baptism.  In doing so, He "announced" the taking of all the impurities of the water upon Himself, i.e., our sins.  

2) He made an act of faith before His Father in Heaven, in which his submersion foreshadowed being buried (submerging), and rising again (emerging).  

In this way, baptism was no longer a sacramental, but a sacrament -- a vehicle of sanctifying grace by virtue of Christ blessing the waters and taking upon Himself the debt of our sins.  

When He emerged from the water, something new took place:  the Holy Spirit appeared and the voice of the Father proclaimed the eternal Sonship of Christ, in order to show that every baptism henceforth would bring the anointing of the Holy Spirit, and make us all sons (and daughters) of the Father.  

Why is Baptism Necessary for Salvation?

Baptism frees an individual from the debt of Original Sin.  As Christ was buried and rose again in victory over Death, each one of us is "buried" in water (i.e., "submerged"), cleansed of sin, and "reborn" as adopted children of God.   As members of God's family, we are entitled to an inheritance.  That inheritance is eternal life.  
 

I've Baptized My Child -- Why Do They Need Any More Sacraments?

Although Baptism entitles an individual to Eternal Life, like any family dynamic, one can lose their inheritance through separation.  We call that separation "mortal sin".  When your child reaches the age of reason - seven years old as reckoned by the Church - they become accountable for their ability to choose or reject sin.  As they grow older, the graces present in the Sacraments of Penance, Holy Communion, and Confirmation will strengthen them to persevere in the pursuit of holiness and rejection of evil, and ultimately bring their baptismal garment "unstained" to the House of God when they leave this world.  The greatest gift a parent can give their child is not a material bequest, but a life of grace through active participation in the life of the Church, where Jesus Christ meets us in the Sacraments with His unfathomable mercy and love.  
 

I Want My Child Baptized in a Catholic Church, but I Don't Intend to Raise Him/Her Catholic.  Is this okay?

No.  Through the Catholic sacrament of Baptism, responsibilities pertaining to participation in the life of the Church are placed upon the recipient as they reach the age of reason and beyond.  Although it is at the discretion of the pastor, Canon Law recommends delaying the sacrament until and unless a sincere intent to provide at least a bare-minimum Catholic upbringing is demonstrated.  
 

Can I Baptize My Grandchild Without the Consent of My Son/Daughter?

Consent of the parent(s) is required for an infant to be licitly baptized in the Church.  Although anyone can baptize using the proper form, matter, and intent of the sacrament, it is illicit and sinful to do so in secret or absent a situation where a child/infant is in real, immediate danger of dying without the sacrament.  In such a circumstance, consent of the parent(s) is not required.
 

What Happens to Children Who Are Not Baptized, Such as the Unborn?

The first commission given to the Apostles prior to Christ ascending to heaven, was to "go forth and baptize all nations".  The Church teaches that the sacrament of Baptism is necessary for salvation, and that does not change with regard to infants, the unborn, and any children who have no means of becoming baptized.  The Church on earth is constrained to the sacrament -- and it is the will of God that the Church baptize.  However, the direction of the Church to baptize is not a limit placed on God to provide baptismal grace to those, who through no fault of their own, could not receive the sacrament.  

In other words, the Church exhorts the faithful to place their sincere faith and hope in the Mercy of God for those fetuses, infants, and children who depart to eternity before they can be cleansed here of Original Sin. 

Note that there is no official doctrine that is required to be held by the faithful on this matter -- indeed, it is licit for the faithful to also hold that these souls are in Limbo -- a place of perfect, natural bliss, but deprived of the Beatific Vision.  But the Church in recent decades has tilted away from Limbo and towards the unfathomable Mercy of God in providing baptismal grace to those who have no personal sin, only Original Sin that was impossible to remove.