Legacy decks are faster and more disruptive than ever, and you can easily be at only 13 life or less on turn 2 when facing a Zoo player (Steppe Lynx you for 4, Chain Lightning and/or Lightning Bolt you for 3, fetchlands, etc.)
In Celebrations, the entire of the main set is Standard-legal, and so are most of the promo cards that come in tie-in products
You can send it at something's face for a lot of damage
Blood Artist is still one of the best creatures that trigger when opposing creatures die, and it has been an aristocrats staple card ever since its printing
Several factors influence POP Series 3 card values: card condition (mint cards worth 3-5x more), rarity (holographic and rare cards command higher prices), first edition status, PSA/BGS grading scores, and market demand for specific Pokemon