One of the most important functions of the church is to serve as a place where people can fellowship; where they can build lasting relationships with other Christians. If you make good Christian friends, then they can serve as a constant source of positive peer pressure and as a support group in times of need. If you've ever dealt with someone trying to break out of bad habits (a life of crime, gangs, drug use, etc.), then you know that the number one most important factor in rehabilitating that person is to get them away from their old friends and help them establish themselves in a new environment where such things are not acceptable and friends help him become a better person rather than go back to old habits.

Acts 2:46 tells us about the first church:

Every day they continued to meet together in the temple courts. They broke bread in their homes and ate together with glad and sincere hearts

Fellowship has always been an important part of the Christian church and continues to be an important part to this day. It would be a very bad idea to give that up.

As an added bonus, it helps make it easier to invite non-believers to church and get them involved. It's a lot easier to invite a friend to a pizza party or theme park night than it is to invite them to a church service.