I'm putting these two descriptions together because in most cases what is understood as "nominal Christianity" is actually "unbelief". So these are the kind of folks that don't believe what the Bible teaches about God, man, history, worldview, etc. and continue to maintain that they are actually Christians.
This reminds me of a conversation I had recently. The young man I was talking with said that he believes in the Lord Jesus Christ and worships Him. As the conversation carried on he explained how he views God as an entity that will just give him whatever he wants.
For example he said that he thinks that if he would pray for a car God would give it to him. I asked him if God ever has given him a car in response to a prayer like that, and he answered, "No." I then told him that this is not how the Bible represents the Lord, and he understood that; however, he said the this is how he is going to continue to approach God, because it makes him feel better.
So as we continued to talk I explained that just because something makes you feel better for a time does not mean that it is based in truth and is good. We can easily deceive ourselves. Our perception often times is different from reality. We also discussed how he likes to think about Jesus. From a lot of what he said it was clear that he was worshipping an idol that he had made Jesus out to be, not who Jesus Christ is in reality (according to the Bible). Also, he is pretty proud of some of the sins that he has committed in his life...because ultimately God used those sins to bring about good. He didn't understand, though, that this did not make the sins a good thing...but in God's common grace He will often use bad things or circumstances for good.
I explained then that if he is worshipping a man-made idea of who Jesus is (in contrast with who Scripture reveals Jesus to be) and he is not willing to repent of his sins...that his life is not consistent with what the Bible teaches a Christian is. He completely understood, and he said, then, that he is not a Christian. But he said that he is going to continue to call himself a Christian because it makes him feel better. I asked him if he were to die that night where he thinks he would go, and he told me that he would be going to hell. I explained who the Bible teaches that Jesus Christ is and described that all he needs to do is to enter into a life of repentance and belief...but he was not willing to do that. Although, he insists on calling himself a Christian because he said it feels good.
The reason I spent so much time writing about this circumstance is because this is a classic case of nominalism or someone who calls themself a Christian, conforms themself to the morality of Christianity, yet they do not believe in what revelation teaches about God or repentance and belief.
I have listed this as a reaction to the problems in the church because folks like this are scattered everywhere in our churches. People who falsely believe that they are Christians. If the gospel is not clearly preached from the pulpit, if the gospel is not clearly displayed and spoken of in the lives of those in the local church then people may be seeking shelter in a church because it makes them "feel better." K. P. Yohannen (founder of Gospel for Asia) has a sobering quote that is very true in this regard, "Feeding a man without sharing the Gospel with him is like giving a sandwich to a man on his way to the electric chair…it is, in essence, simply making him more comfortable on his way to hell."
When churches do not embrace a biblical approach to discipleship of all of it's people (those that covenant with the congregation in membership), and allow non-Christians to shelter as if they were Christians (in membership or even attendance) that is a major problem in the church. So you can see how nominalism and unbelief can be supported by the local church.
The young man in the conversation that I wrote about above is regularly attending a church. In the way that the church functions he has never been confronted with his unbelief or the fact that he is not a Christian. This is a problem...and while the church has not caused his nominalism or unbelief it has not helped him see it, thereby contributing to his continuance in unbelief. Hence, his reaction to that basic problem of discipleship in that specific local church has been to continue in nominalism/unbelief.