why we need abstract factory when we already have concrete factories

this is the article

https://www.codeproject.com/Articles/328373/Understanding-and-Implementing-Abstract-Factory-Pa

I don't know why we need to have an abstract factory like IPhoneFactory, in the client's end, can't we do sth like

class PhoneTypeChecker
{
   ISmart sam;
   IDumb htc;
   //IPhoneFactory factory;    get rid of this abstract factory
   MANUFACTURERS manu;

   ...
   public void CheckProducts()
    {
        switch (manu)
        {
            case MANUFACTURERS.SAMSUNG:
                Console.WriteLine(new SamsungFactory().GetSmart().Name()); 
                Console.WriteLine(new SamsungFactory().GetDumb().Name());               
                break;
            case MANUFACTURERS.HTC:
                Console.WriteLine(new HTCFactory().GetSmart().Name());  
                Console.WriteLine(new HTCFactory().GetDumb().Name());               
                break;
            case MANUFACTURERS.NOKIA:
                Console.WriteLine(new NokiaFactory().GetSmart().Name()); 
                Console.WriteLine(new NokiaFactory().GetDumb().Name());                
                break;
        }

        Console.WriteLine(manu.ToString() + ":\nSmart Phone: " + 
        factory.GetSmart().Name() + "\nDumb Phone: " + factory.GetDumb().Name());
    }
}

the only thing I can think of to use IPhoneFactory is that we needs to get two different types(Smart and Dumb) from concrete factory classes, but it only save some keystrokes, isn't it?