These people may pat themselves on the back for their great faith. (Trust me, most do.) They are convinced that having a cursory knowledge of Jesus and the Bible is great faith. Strangely enough, the longer they have been away from the Divine Service, the greater they claim their faith to be. They may even run across other Christians who do the same thing. Each commends the other for their freedom and wisdom in not merely neglecting Word and Sacrament, but for outright ignoring it.
They are lying to themselves. As Martin Luther notes below, merely thinking about Jesus does not save you. You will find no forgiveness in your own ponderings and meditations. It may not be long before you are pondering and meditating the imaginations of your own heart. This amounts to creating your own god, who ends up being (gasp!) just like you!
Dear Christians, do not be deceived. Do not buy the lie. This is what the Lord said to the Pharisees who knew Jesus better than you do but ignored him anyway: "Whoever is of God hears the words of God. The reason why you do not hear them is that you are not of God." (John 8:47) God's people love to hear God's word, and they gather together to hear it read and preached and to feast on his holy meal. They flock to it because they know how much they need it. They love Jesus because he has loved them, because he has lived and died for them, and because he pours out his gifts of mercy and forgiveness to them in the word and sacraments. God's people know that their life is found alone there.
Those who don't come to hear the word and partake in the sacraments make a different confession: They are not of God, no matter how great they insist their faith is, no matter how many works they boast, no matter how much love they ascribe to themselves, and no matter how sincere they seem. Those who say they bear the name of Christ do not deliberately avoid him. They betray themselves. They are not God' people. And they will find no mercy, for they spurn his love and forgiveness.
So why does coming church matter?
Martin Luther says: “We treat of the forgiveness of sins in two ways. First, how it is achieved and won. Second, how it is distributed and given to us. Christ has achieved it on the cross, it is true. But he has not distributed or given it on the cross. He has not won it in the supper or sacrament. There he has distributed and given it through the Word, as also in the gospel, where it is preached. He has won it once for all on the cross. But the distribution takes place continuously, before and after, from the beginning to the end of the world. For inasmuch as he had determined once to achieve it, it made not difference to him whether he distributed it before or after, through his Word, as can easily be proved from Scripture… If I now seek the forgiveness of sins, I do not run to the cross, for I will not find it given there. Nor must I hold to the suffering of Christ, as Dr. Karlstadt trifles, in knowledge or remembrance, for I will not fid it there either. But I will find in the sacrament or gospel the word which distributes, presents, offers, and gives to me that forgiveness which was won on the cross.” (Luther’s Works, American Edition, Vol. 40, page ___)