Well, having Pokemon eggs use their own species' design would mean many more resources. That's about 300 (just a guess) individual eggs that serve no other purpose than to look pretty.
And I couldn't find the link or blog article, but Junichi Masuda has said that they prefer not to have the anime voices/sounds/cries for Pokemon in the games. That would be a lot of work and really would have little impact on the game. Plus, there's the fact that a Pokemon might have 5 different language voices, or it might keep its original voice, or the person portraying the voice might not be the same as it used to be. All in all, it's a complete nightmare to try and do except for specific Pokemon, like Pikachu.
And I couldn't find the link or blog article, but Junichi Masuda has said that they prefer not to have the anime voices/sounds/cries for Pokemon in the games. That would be a lot of work and really would have little impact on the game. Plus, there's the fact that a Pokemon might have 5 different language voices, or it might keep its original voice, or the person portraying the voice might not be the same as it used to be. All in all, it's a complete nightmare to try and do except for specific Pokemon, like Pikachu.