I think there are a total of three important reasons why you should use this site:
First, it helps your deck building abilities, since you will find not-so-obvious synergies (Missile Launcher & Venomizer for 8 mana board wipe, or Meat Wagon and a magnetic card to "control" the recruiting of the deathrattle effect).
Second, it helps you with your actual gameplay (like the Meat Wagon example). It is also very important to know what removal options your opponent has at various mana costs to play around them.
Third: You landed here because you want to improve yourself. You can do this by repeating quizzes (through "Rote learning ") wherever you are and whenever you want.
How are you doing?
Molten Giant (Legacy) (98.61%)
Conceal (Legacy) (98.55%)
Lay on Hands (Legacy) (98.46%)
Tundra Rhino (Legacy) (98.41%)
Power Overwhelming (Legacy) (98.41%)
Alexstrasza (Legacy) (98.39%)
Hex (Legacy) (98.39%)