Is evolution necessary? No....*sigh* whatever.
But are ALL the reasons to not evolve a Pokémon legitimate? No. Some are some aren't.
Pikachu's reason- It doesn't want to evolve to get stronger. That's such a BS excuse, I get that there is a time to prove one's self as is and not, but I think this message was horribly done. Because it feels like an insult to those who did evolve. Oh you had to evolve to get stronger, whoop de doo, you weak sauce creature. Maybe if the message was.....actually there's no right way of doing because in some way it'll always insult those who didn't evolve.
Bulbasaur's Reason- It wasn't ready. That's fine, but the problem seems to be that Bulbasaur refused to evolve, because was Ash was a "jerk" (that's way too soft a word) and Bulbasaur didn't like Ash's attitude. I can see how Ash's happy attitude would be insulting. "NO, I don't want a Bulbasaur, give me Ivysaur" I can see why Bulbasaur evolved.
Piplup's reason- I have no idea what the hell Piplup's reason was (because I can't trust either the dub reason or what people say is the Japanese reason) but it was such a B.S. move to pull in the same series as Pikachu refusing to evolve. Granted there was no right way to do it but still. Maybe it should've been Piplup who refused to evolve PRIOR to the episode of Pikachu refusing to evolve.
Any other reason- I just don't think there really is any reason for a Pokémon to remain unevolved, that's legitimate. Maybe size, weight and appearance could be used, but that's such a shallow reason to not evolve, I'm looking at you "ShinyCharyzard."
Especially for those who don't evolve because their forced to stay unevolved by the writers.
I can agree, that unevolved Pokémon can be strong, but I still believe their evolved form will always be superior in strength (if not speed).
And before you argue: I mean Ash's Raichu (for example) will always be stronger than Ash's Pikachu.
I don't give a rat's rear end about Lt. Surge's Raichu, or Sho's Raichu, or whoever else has a Raichu that could lose to Ash's Pikachu.
And also what Joltik-Kid said, evolution, and new moves are the only ways you can develop a stagnant Pokémon late in the story, without resorting to fake development. If a Pokémon can't evolve, then fake development is fine. But for unevolved Pokémon, any serious character flaws that need to be overcome needs to occur early in the story (depending on the circumstances) OR it looks like fake development.
Oh no suddenly Snivy has a fear of fire? Oh no Oshawott is somehow suddenly kicking butt? Oh no....okay forget that last one. But whatever.
Misinterpreting my posts is not your fault, negative repping me, and getting very sensitive about my posts because you misinterpreted my posts however is your fault. Think really hard, before negative repping or making a big deal about my posts. I don't appreciate being negative repped for reasons that are a result of misinterpreting my posts.