Gameplay, flavor, fandom, fun drafts, and good ol' classic broken cards
You can check out our guide to Magic: The Gathering Booster Pack types here, but the short version is that Collector Boosters are filled with alt art, foil treated and special variants of cards in any given set
The problem is that a 2/2 (even a 2/2 with flying) can be outclassed fairly quickly, so delaying Vexing Gull trades its early game relevance (pecking in for damage) for mid-game value (when you might be behind in the race or not be able to attack with Vexing Gull)
Return all land cards from your graveyard to the battlefield tapped
Need that Counterspell
(See?) An effect that allows you to put an artifact card from your graveyard onto the battlefield wouldn't affect Sword of the Realms, however: a modal double-faced card has only its front side's characteristics while in the graveyard