Before the Eidolon Orb store, anyone joining the game after... humm, let's say Amalthea, simply wouldn't have access to an elemental Wind Eidolon. At all. Not until Garuda reprint anyway, which is almost a full year after Amalthea. That's a huge loss, and would certainly be a massive detriment towards new player picking the game up. Okay fine, there's Pazuzu, but Pazuzu for a new player is... not... quite... uh. Yeah.
Anyway. Enter the Eidolon Orb Store. It gives newer players an inconvenient - but yet possible - method of obtaining powerful main SSR Eidolons. Like +elemental and +char/HP Eidolons. At the same time, it was great for veterans since it gives access to all Kaisers, with their great on-uses. And even whales should be thankful for those Kaisers.
But what's the goddamn point if they don't update the Shop to have all the +Char/HP and +Elem/stuff Eidolons? Like Yule Goat, or freaking Vlad, the single most important universal farming Eidolon in the game? Well, I guess Vlad is debatable since the effect hasn't been proven.