The language fictional characters use is chosen for effect, at least if the author is concentrating.
“'Cause I was already a smoker, it was easy to get addicted. The one thing that they don't teach you about marijuana is how addictive it is.”
“Well, I - all cases to me have interest. Every case is important to somebody, the people litigating that case. But the most difficult case for me is the case where one person says a, the other person says b, and you just don't know for certain who is not telling you the truth.”