>>42016788DESU that was one of the best things they could do. National Dex's only reward was that feeling of completition and effort. Back then, you could brag about rare mons like the Johto starters, Bagon, Milotic, the "!?" Unowns and Porygon because they were either hard to obtain or extremely rare.
They had to implement all those Pokemon in an organic way, so they couldn't just slap Mewtwo or Celebi in Hoenn.
You could perfectly complete the Hoenn Pokedex with only RS; FRLG were for the whole Kanto dex, and the few Johto Pokemon remaining were obtainable since Colosseum (except for Lugia, but since it couldn't be obtained on the mainline games, it was considered like a Mythical in the games). Emerald and XD just made the job easier (in fact, only Emerald and XD allow you to complete the Hoenn Dex excluding single-encounter mons like the starters or the other Lati).
In short, although it was a pain to complete the Pokedex, it was also the fun part, as it actually required effort and completing various games. Also, each of those games were different and had different focuses: Kanto appealed for the nostalgia; Hoenn was the new thing; and Orre was a more challenging experience, not just a straight path and an uncomplete open-world attempt.
