Pichu didn't exist until the second generation of games, a year after Yellow's release. Also, the Pikachu you receive in the game is unable to evolve into Raichu unless traded to a different version and then back to the original game. So, in the context of being a starter pokemon, Pikachu effectively has no evolution opportunities.
for marshtomp i kept putting marshtop
for some reason, i thought chikorita had a q
i knew what they all looked like but couldnt remember the names
https://www.jetpunk.com/user-quizzes/235686/pokemon-starters-and-their-evolutions-gen-1-8