The main thing is that Christians should have a personal relationship with God, but this will be easier to achieve if they attend Church. For Roman Catholic and Orthodox Christians, and to some extent for Anglicans, participating in sacraments is important. By participating in Baptism Christians are cleansed of Original Sin and reborn to new life in Jesus. By participating in Communion Christians are redeemed from sin and death. Sacraments can only be administered by a Priest – usually in a Church – so if a Christian does not attend they will miss out on the outward signs which can trigger inward spiritual changes in their relationship with God. In addition, attending Church helps Christians to bond with the wider Church community. Church gives the opportunity to learn about faith; those who do not attend may be more likely to sin. Church also gives an opportunity to put faith into action; the Letter of James teaches “do not merely listen to the Law – do what it says” and “faith without action is dead.”
Clearly many Christians would disagree. In the UK, Church attendance is at a historic low. Christians who do not go to Church may argue that liturgical worship is boring, that non-liturgical services add little to their relationship with God or that informal music-based worship might even be a distraction. Jesus did not attend Church, yet managed to develop a close relationship with God. Nevertheless, these Christians underestimate the value of praying together with other Christians. Jesus told his disciples that “whenever two or three are gathered together in my name, I am with them” (Matthew 18) suggesting that He may not always be with people who pray alone. Further, Quakers do not have liturgical services and do not use sacraments and yet still meet regularly to worship in silence, valuing the focus and spiritual support that this gives them as well as the sense of community.
In conclusion, while it is true that developing a personal relationship with God is the most important part of Christianity, it is easier to do this through attending Church than by not.