One of the reasons why “all the good cards are rare,” is because people have a hierarchy in mind. I believe that customers, Magic designers, and myself included, think uncommon cards should be “better” than common, and rare cards should be better than uncommon. This mindset is tied to the meaning of the words common, uncommon, and rare.
People prefer diamonds over cubit zirconium because diamonds are more rare. Gold is better than copper because it is rare. Money is only good because it is rare, if everybody was a millionaire, money would be NOT worth as much. Mark Rosewater, a Magic card designer, said that it is getting harder, and harder to design new common cards. He compares the card rarities to an ice cream Sunday. The commons are the ice cream. The uncommons are the sprinkles and the rares are the gooey, sweet, hot fudge. You can’t just have all hot fudge; well that is what he says.