"Dialogue trees aren't for deciding who you are (they might, but indirectly and it isn't their primary purpose). They are for deciding what you say when that matters."
What you say defines who you are for others. Because... you know... people use words... well, you know - to understand each other. It depends on your PERSONALITY TYPE/ATTITUDE what exactly are you trying to express through WORDS (Well, unless you're hoping for some sick game where you're supposed to be a mean fuck who tortures himself with telling kind words...).
"If you had, you wouldn't have asked that question."
Nope, It's the truth.
Kinda like i can tell you are a fucking idiot just by reading your bullshit?
Dialogues dont decide who you are, not really. you can be an evil motherfucker that just masks himself as a good guy, waiting for the trust to grow and the time to strike for maximum profit. you can just be a liar, or you can be a tough good guy that speaks with actions and not words. And all that cant be realistically represented with just dialogue alone.
Dragon age never gave you a personality, it gave you a stance on a matter amongst several, but you were always the same prick, especially on dragon age 2.
What would have given you a "personality" would have been selecting 1 personality out of 3 and playing the whole game with the predetermined answers for that particular choice. There are other (better) ways, but well, i dont want to write a wall of text.