Kids who just want to buy the pretty card of their favorite Pokmon are unable to buy product in stores, and are wildly priced out of buying them as a single
Update (April 8): Explained the state of the meta in light of Shining Revelrys arrival, which has added new best cards to consider for any deck
I had the various Orbs of Dragonkind in the deck, but eventually cut them for more Dragons, except for Jade Orb, since it gives hexproof to whatever Dragon you cast with its mana, helping to ensure its survival until your next turn

Sort Rarity Card Type Ho-Oh #1Holo Rare $0.28 Reshiram #2Holo Rare $0.29 Kyogre #3Holo Rare $0.27 Palkia #4Holo Rare $0.23 Pikachu #5Holo Rare $5.65 Flying Pikachu V #6Ultra Rare $3.97 Flying Pikachu VMAX #7Ultra Rare $7.29 Surfing Pikachu V #8Ultra Rare $4.62 Surfing Pikachu VMAX #9Ultra Rare $7.67 Zekrom #10Holo Rare $0.30 Mew #11Holo Rare $3.30 Xerneas #12Holo Rare $0.27 Cosmog #13Holo Rare $0.33 Cosmoem #14Holo Rare $0.29 Ponyta #14Promo Lunala #15Holo Rare $0.37 Zacian V #16Ultra Rare $0.70 Groudon #17Holo Rare $0.24 Zamazenta V #18Ultra Rare $0.74 Yveltal #19Holo Rare $0.18 Dialga #20Holo Rare $0.24 Solgaleo #21Holo Rare $0.30 Lugia #22Holo Rare $0.64 Professor's Research #23Holo Rare $0.17 Professor's Research (Full Art) #24Ultra Rare $1.26 Mew (Secret) #25Secret Rare $68.18 Mew (Secret) #25Secret Rare $68.18 Surfing Pikachu VMAX #9Ultra Rare $7.67 Flying Pikachu VMAX #7Ultra Rare $7.29 Pikachu #5Holo Rare $5.65 Surfing Pikachu V #8Ultra Rare $4.62 Flying Pikachu V #6Ultra Rare $3.97 Mew #11Holo Rare $3.30 Professor's Research (Full Art) #24Ultra Rare $1.26 Zamazenta V #18Ultra Rare $0.74 Zacian V #16Ultra Rare $0.70

Since the basic lands are the calling card of Un-sets, having "just another" set of full-art lands is a bit of a disappointment
Searching for a correlation, the appeal of the character on the card seems to be the biggest factor