Also because you can play cards you love even if theyd be terrible in a strict 1v1 format
I am pretty sure that people playing in competitive tournaments on MTGO couldn't care less about Commander cards, but hey, I don't have the market research that WOTC has
Because you get to choose who gets to draw with you, you can make a short-term alliance with one player, protecting you for a few turns or forcing another player to spend a coveted counterspell to put a stop to it
For 1 mana, you can draw two cards and discard two, acting as a good filter for your cards
You can also add a third card to this loop to fully break it something like Archangel of Thune or Conclave Mentor will let you supercharge every creature on your board to arbitrarily large stats and cruise to victory from there
Yes, dungeons are a special card type that never goes in your library and is initiated by specific cards