Why does ASP.NET MVC 4 SimpleMembershipProvider keep creating aspnetdb.mdf?

When you create a new ASP.NET MVC 4 Internet Web Application it creates a nice template with authentication enabled with new SimpleMembershipProvider It contains InitializeSimpleMembershipAttribute class which creates built-in Entity Framework Code First database and initializes Simple Membership:

using (var context = new UsersContext()) 
{
    if (!context.Database.Exists())
    { 
        // Create the SimpleMembership database without Entity Framework migration schema       
        ((IObjectContextAdapter)context).ObjectContext.CreateDatabase();
    }
}
WebSecurity.InitializeDatabaseConnection( "DefaultConnection", "UserProfile", "UserId", "UserName",  autoCreateTables: true);