That is because in Judaism beliefs are not nearly as important as what a person does. In that respect I think Judaism is better than Christianity.
I have to disagree with DJW here.
In order to correct this common view, Jesus three times told Nicodemus that he must be born again.
Belief precedes sin, not the other way around. Jesus is starting to address the sin nature from the inside, not the outside. Christianity is not about trying harder, running faster, of jumping higher. It is not wrong-behavior modification, it is wrong-behavior death.
This is related to the topic because what actually happens when we decide to believe God and everything he says, he gives us a new identity, a new personhood - and a new spirit, which is one of the three parts that make up our beings. We are made in God's image who is also a tri-partite being.
Just so people wouldn't try to foolishly work their way into God's grace through good works, Jesus made it clear that just looking a woman with lust would make you guilty of adultery.... which every Jew knew carried the penalty of death I might add.
by the deeds of the law there shall no flesh be justified in his sight - Rom. 3: 20
Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified. - Gal. 2: 16
God has made it clear in his word that we are not allowed to work in any way, shape or form for our salvation. If we persist in doing so, we are only racking up more debt that we will personally pay for on Judgment Day.
Now to him who works, wages are not given as a gift, but as a debt. But to him who does not work, but believes in Him who justifies the ungodly, his faith is credited as righteousness. - Rom. 4: 4-5
But go and learn what this means: ‘I desire mercy and not sacrifice.’ For I did not come to call the righteous, but sinners, to repentance.” - Mt. 9: 13
God gives us a choice. In Christianity, God seeks to destroy the sin nature, not simply modify it. We merely decide if we are going to give him permission or not. He does it all.