>>53351856At least for the initial implementation of baby pokemon, it's because they didn't add very much. Pokemon like Pikachu, Clefairy, and Jigglypuff were already early-game pokemon that could be caught on fairly early routes. Some of the other Gen 2 babies, like Tyrogue, Smoochum, Elekid, and Magby, evolve into rarer and stronger pokemon that were only available in the late to midgame, though in Gen 2 you could only get the latter 3 through the Odd Egg, and Tyrogue was pretty deep in Mt. Mortar.
I think Gen 4 and 5 demonstrate a good use case for them though, with how Budew was available before the first gym, and how BW2 had Elekid and Magby as other early options you could catch. That gives baby pokemon more of a purpose, where it's essentially improving the availability of a late-game pokemon by giving you a weaker version sooner.
The main flaw is when the games don't use babies in that way, and instead give you a weaker version of a mid-game pokemon in the mid-game, leaving you to just question the purpose.
I'd also say it's also somewhat better in the cases where the baby is introduced in the same Gen, like with Togepi, Riolu, or Toxel, since then it's more of a typical mon where it's just a case where the first stage can't breed, rather than a revision to an existing pokemon which might be more scrutinized as towards the reason.
