>>20262755>on what purpise?It's my theory that, since Unova is almost like a reboot of the series, that they made the starters underpowered to encourage players to use the multitude of new Pokemon available to them. There are easy replacements early on (Petilil, Darumaka, Tympole).
Seeing as all the starters in Gen IV were incredibly viable in-game (and at the time, out), they probably went a little overboard in insuring they wouldn't be overpowered.