This isnt just to sell cards, though that was a huge part of it, but more importantly, it was just because new cards are fun and players are excited to get to use them
There are basic Energy cards (like Fire, Water, Grass, Lightning, Psychic, Fighting, Darkness, Metal, Colorless, Dragon, and Fairy, although Dragon and Fairy are now typically represented by other types or Colorless in modern sets) and special Energy cards, which often provide additional effects alongside energy
The life loss isnt much of a downside, but it can be painful if you need to remove a Doubling Season or Warstorm Surge
Energy cards, which are attached to Pokmon to fuel their abilities, are randomly generated each turn so players will no longer find themselves cursed with no energy in their hands
Core Set Booster Rarities There are four core booster packs released each year in Yu-Gi-Oh, and for the most part they follow the same rarity distribution