Why are most of the pages of the core Pokémon games not merged?

[Tokkar200052]

I was looking up Music for Game Boy games and found out that Pokémon Blue, Red and Yellow and Pokémon Crystal, Gold and Silver are not merged together even though they have the exact same music and are nearly the same games. Should whoever is in charge merge the pages? Is there a reason why the core games of the same gen are separated?