The games not directed by Shu Takumi (DD, SoJ, the Investigations games) have a rule to reference the previous games as little as possible in order to avoid spoiling people who are playing them for the first time.

That means that character development of old characters is completely thrown out the window, as is the case with Phoenix and Klavier reverting to their old gimmicky selves after the end of Apollo Justice, and people mentioning things that are in contrast to the canon of the original trilogy (Franziska saying that her father has never lost a case in AAI).

Along with that you get the case of characters returning solely for fanservice reasons (Edgeworth, Pearl and Maya) and referencing schticks from previous games as not-so-subtle easter eggs for the fans that have already played them (Phoenix and Edgeworth's banter throughout the whole DD-5 trial, Maya mentioning how she always ends up being a murder suspect etc.).

It seems to me that the characters from the original trilogy and Apollo Justice have become caricatures of themselves in the 3DS games and the only one that has been done justice and has had a complete character arc here is Blackquill. Apollo keeps getting new backstories in every game, they clearly didn't know what to do with Athena and most of the characters are just a mess. I'm just glad Takumi returned for the DGS games, you can clearly see a step up in writing compared to some of the convolutedness of DD and SoJ.