Because he is the Son of God, and not God.
If you read that verse that's always quoted…"I and my Father are one".
1.) Look at the verse IN CONTEXT. It is OBVIOUS that Jesus Christ is saying that they are ONE IN PURPOSE!!!
2.) Otherwise, why would he say "I AND MY FATHER"??? He didn't say I AM GOD. He said I and my Father are one in purpose (in context).
The other verses ( OVER 200 ) that tell us that Jesus Christ is the Son of God are all IGNORED! Is that logical?? Why ignore so many verses that tell us that Jesus Christ is the Son of God and cling to one verse TAKEN OUT OF CONTEXT!
And if you try and argue this with them they take you in circles. That is because the entire "trinity" theory is based on MANS CIRCULAR ARGUEMENT. Just go ahead and read the Trinitarian Creed. It's psychosis to believe in it. Yet the Catholic Church forces ALL CHURCHES that want to be recognized as a church and get "funding support" etc, they MUST agree to this creed.
BTW, the creed never even once references the Bible, not one verse. The Catholic Church makes up it's own man-made religion that is ALL LEGALISTIC.
God showed man that the 10 Commandments were merely to show man that he cannot cleanse himself and never break a law (i.e. never sin; reed Romans). It showed man that they needed a Savior, hence Jesus Christ. God says that Jesus Christ fulfilled the law. He HAD TO BE A MAN in order to do that.
There is so much to this, I can't get into it all here on QResearch, but you need to go back to the fall of man and realize that Adam, when he transgressed against God's ONE request, he lost his Spirit. Genesis 3:15, God then promises a Savior for man.