Churches.   And why have them.

What are they?

        They are the places where people who share a belief in some deity - some god - meet especially for business to do with that god.
        And they are also said to be the shared belief itself.  
        So that if you share the belief you're said to be 'in the church' even if you're not in a building.
So a church can be a building - any building - but it doesn't have to be.  It can be just the beliefs shared by a group.

        I suppose a belief held by only one person would be a church of one.

So it looks like we will always have churches.
Because we will always have people believing something or other.

        Ah...   but a church should be about god.

Yes, sure.  Well, same thing,  we'll always have people believing something or other about god.