you can test the behaviours and the reactions of people to your thoughts, your way of speech, your (virtual) actions. Based on a "medium" people, it can be useful to shy people to become more confident. And it can be a funny game to do with the own real partner: she/he could be jealous of the AI!
Maybe yes, of course. It's the same risk of porn movies or to pay for sex, right? They can be some shortcuts to gain some "features" of a relationship without engagement.