Also, why not tell someone what I think they're thinking?
Because unless you have a lot of interaction with a person so that you know them that well you are being rather presumptive, arrogant, and when it isn't even close to what they are thinking it can be rather annoying that the person has the audacity to assume they know what you are thinking. It is naive, it is arrogant, etc.
Why not ask if they are thinking something rather than telling them what they are thinking? That simple change can make all the difference in the world. One way can make you come across as a knowit all asshole, and the other actually ASKS rather than assuming. Also consider TELLING people what you are thinking and then going off and writing or saying a lot of things based upon that is an incredible waste of time if they were not thinking that at all.
Bursting people's bubble can help them expand their horizons.
Yep I like to bust the bubbles of people who think it is okay to imply they can read minds. ;)
You can do WHAT you are implying as far as bubbles by ASKING rather than assuming. That's a big part of the socratic method. :) Sure it may slow you down while you wait for an answer, but personally I think that is better than totally misrepresenting someone elses thoughts and going off on some long discussion based upon that misrepresentation.
I did mention that I'm telling them what I "think/interpret" them to be saying, while obviously being open to other alternatives.
In other words, I'm not saying "Hey, you are thinking this and that's that! Don't try to tell me otherwise!". Indeed, that would be arrogant. What I'm saying is "Hey, from what I've seen of you thus far, it seems likely that this is probably what you're thinking in these particular regards. Are you?" Of course, the question and the answer can be expressed vocally or/and more indirectly, through non-verbal means.
Personally, I don't care about how people see me and I'm always myself when interacting with anyone, as I consider honesty to be one of the more advanced forms of genuine, natural respect towards both one's self and others. While some people have been put off by this (which is their freedom, by the way), I've also met people whom I would call genuine companions. However, that was more of a welcome side effect, but making close acquaintances wasn't ever my interest.
Anyway, why wait for an answer to come straight from their mouths? I mean, yeah, they can be honest about their thoughts, but there are also situations where one might either try to be manipulative or/and maybe not know themselves well enough. Regardless of any interpretations' level of accuracy, it's still a nice way to exercise the analytical parts of the mind (whichever level of mind we might be talking about).