In season 1 of Pokemon, virtually all of the nurse Joys had their own Chansey. When generation 2 came around, one of the new Pokemon introduced was Blissey, the evolved form of Chansey. Chansey is a happiness evolver, which leads to my question. If Chansey evolve through happiness, how did none of the Chansey in Kanto everevolve prior to the introduction of generation 2? Were all the Chansey in Kanto just neglected or abused?
I highly doubt this is the in or out of universe explanation, but, since there is no other explanation, we only have conjecture to base this on.
However, before you accept your theory as the truth, consider that Pokémon have a choice when evolving.
In episode 14, when Ash's Pikachu loses to Lt. Surge's Raichu, Ash attempts to evolve Pikachu by means of a thunderstone, to which Pikachu declines. Perhaps the Chancy wish to remain chancy for whatever reason, but like I said, we can only assume as there is no answer.
A couple of things to note:
The Johto region, and by extension Blissey, didn't exist at the time those episodes were made. As far as everyone was concerned, Chansey was a fully evolved Pokemon.
Chansey don't evolve simply by being happy. As with all happiness evolutions, the Pokemon must level up whilst having a high happiness rating. In the anime, Pokemon can evolve outside of battle, but this tends to be to protect their trainers from harm. Even if we assume that the Nurse Joys have caught their Chansey with Pokeballs and are effectively their trainers, I don't suppose many Nurse Joys have been in that amount of danger, nor do they seem the battling type. Therefore, it's not much of a surprise that there are mainly still Chansey in Pokemon centres and not Blissey.
So, to answer your question, no, Nurse Joys aren't neglectful. Their Chansey just don't have a reason to have evolved yet.
Besides, have you ever seen a Nurse Joy? I don't think they're capable of being anything other than caring about each and every Pokemon they encounter.
I'm going to start off by saying this is one of the many differences the anime has from the canon games. In the games, there's a fixed condition as to when a Pokémon evolves, whether it be at a certain level, trading, certain item etc. However, in the anime, this is different.
Pokemon get to "choose" when they want to evolve in the anime. I suppose it's for comic relief. I mean, a Bulbasaur doesn't look as cute as a Venusaur now does it? An excellent example would be Ash's little green friend.
Its biggest fear appears to be of its fully evolved form, Venusaur, demonstrated in Island of the Giant Pokémon and The Ghost of Maiden's Peak, both times where it was paralyzed in fear by fake Venusaur. Interestingly enough, it defied the wishes of the first real Venusaur it encountered, demonstrating that Bulbasaur is a courageous Pokémon when standing up for something it believes in.
This applies to many other Pokémon we meet throughout the anime and it's the same for the Chanseys. They just don't want to evolve, it's not because they were neglected. I highly doubt Nurse Joys, the people in charge of caring for Pokémon, would let their own Pokémon be neglected.
Chansey is similar to her Trainer, Nurse Joy, as both are caring and nice to Trainers and Pokémon.