The single green mana requirement means that it can be jammed into many decks, and often will be found as the only green card in a 5 color deck
Anytime another player asks how many cards you have in hand and its more than them, you know youre in a good place
Many cards in this deck are pretty weak on their own, which means the opponent can easily counter if they have more powerful Character cards, particularly in the late game
3 Celestine, The Living Saint - Forces Of The Imperium Despite the wings, halo, and a massive golden sword, Celestine, the Living Saint is a powerful human commander with tons of creative interactions with lifegain mechanics
Wizards of the Coast apparently doesnt want to lend too much aid to the secondary market, because the game client features no auction system, no direct transaction of currency between users and no autosell function like certain trade stalls in MMORPGs