User blog comment:Skardae/Some Questions/@comment-24971427-20150929152659

You run Size 1s, because the Size limit is 3, so if you call a Size 2, you can only call Size 1s and 0s, not calling them would be a waste. Just because a card is good doesn't mean it's better than all the other cards out there. The investment spent in a Size 3 could be easily wasted by a simple card like Demon Lord, Asmodai and a Speed Summon.