Theyre happy to mill or discard this card early for a finisher later
Being able to eat multiple cards each turn is hugely important when it comes to keeping Delve cards like Treasure Cruise or Murktide Regent in check
Also, considering you can use fusion material from the deck when the opponent controls an Extra Deck monster, you can easily put the opponent in situations where they need Extra Deck monsters to beat you, especially since they probably wont expect you to use Shaddoll Fusion in your deck to begin with, causing that requirement to be met
For example, cards featuring popular Pokemon or from sought-after sets can fetch high prices because they are in high demand
You can get a pretty big HP boost from that but it's quite costly
However, that raises the questions of where to start, and how easy each game is for new players to learn