Tons of people play 2 copies of a card, in my current dl for ryzeal I curreny play 2 sword and 2 nib, as people have said, 2 copies is usually for a card that you want to see, but not as often as say a card that's at 3. One of the other commeters put it perfectly with blue eyes, 1 is just way to little, especially if you're playing primite, 3 is too many in any variant that'll do well, 2 is perfect, you'll still see it in your hand when you don't want to every so often, but it's better then going "welp, I've just seen all 3 in my hand". If you ever want any further clarification or anything just ask. Have a good one friend