I seriously don't know why people are against the option of creating and controlling the RP of multiple characters
Because majority of playerbase is not schizophrenic and doesn't really fancy talking and debating with themselves in a RPG (which is what the absurd dual dialog is in SP) Aside that I fully agree with your post. As long as it is optional it is no problem at all. But it wasn't optional in D:OS. On release day there were no (even now half-assed, imo) AI personalities. So you had 2 puppets with about as much character depth as a puddle on the road and if you wanted to experience the full game you had to enable dual dialog, and thus lead schizophrenic debates with yourself over the matter of stolen fishes (woohooooo!) (example) Worse, these dual dialogs did not develop the character, they only affected stats. So as a powergamer you *had* to actually game the dialog and not roleplay..
Mind you, in RPG's I can accept 1 puppet, aka 1 char that does what I want* and says what I want* (with the restrictions of his defined history and backstory) but D:OS pushed it too far by making the 2 puppets not just identical from the outset but also incredibly boring personalities. I honestly wouldn't even TALK to the source hunters as they are portrayed in D:OS and I don't think I would want to fight for "their" side after D:OS either.
To be frank, if it is an option I want to join the side in D:OS 2 that fights source hunters.
Anyway, this is all long debated to death. As long as a 2nd puppet is optional no problem...