You do realize that there are Christian groups that worship together outside of a church building, right?
Not everyone who attends church (as you define it) is a Christian. There are plenty of Hmong who do so because they don't have a clan and their main worry is that nobody will give them a proper funeral. Some people start their own church to preach their own beliefs that aren't even biblically supported. We usually label them as a cult. Some are seeking a group to belong to and have a community to hang out with. Nothing wrong with any of that but it also doesn't make them more Christians as you seem to think.
Many churches today have fallen into apostasy and I highly recommend Christians to pray to the Holy Spirit to give them discernment, lest they be following a false god.