The Pokémon video games have been released in pairs since the days of Pokémon Red and Green. This may seem meant to encourage players to buy both versions themselves, but according to the series' creator, the creation of two Pokémon games as counterparts was more about encouraging trading between multiple players with different copies.
Pokémon Red and Green (released as Red and Blue internationally) had 150 Pokémon to catch, but players needed access to both games to accomplish this feat, as some Pokémon were only available in one version. Some Pokémon could also only be acquired through trading, regardless of the version; players only receive one starter Pokémon and one Eevee, and some Pokémon evolve only through trading. The dual-release structure has been kept for every generation of Pokémon games to date, with the most recent being Pokémon Sword & Shield.
Fans could always buy both versions and two game systems to collect all the Pokémon - and some certainly do, likely leading to some extra sales for Nintendo and The Pokémon Company. But the actual reason for Pokémon's paired releases relates to another series that directly inspired the franchise.
Pokémon's Paired Versions Were Inspired By Dragon Quest Frustration
In a 2004 interview on Japanese TV show Dragon Quest 2, Tajiri badly wanted an item called the Mad Cap, which reduced the MP cost of spells. The Mad Cap was extremely rare, only having a 1/128 chance of dropping. Tajiri never found it, while Pokémon artist Ken Sugimori found two. Tajiri wished he could trade an item for one of Sugimori's Caps, but that wasn't possible with the technology of the original Famicom (NES).
When Tajiri discovered the Game Boy's Link Cable functionality, he thought back to the Cap. Its rarity was the key to its appeal, and that was the foundation of the Pokémon games' version exclusives: If a Pokémon was available in one game but not the other, it would automatically be more appealing than if it was common.
Nowadays, the mainline Pokémon games are likely still released in pairs more out of tradition than anything. The ability to trade Pokémon online within seconds means the appeal of trading for rare ones isn't as strong as it once was. Still, Tajiri and his team were certainly onto something huge with Pokémon trading, as it helped turn Pokémon into a social game, where players sought each other out in order to trade and test their mettle in battle. If a new mainline Pokémon generation consisted of a single game, a bit of that magic would be lost.
Source: GameCenter CX
