Yes, a thesis statement is to inform the reader what your paper is about, but it doesn't have to be bland. In my opinion, if a thesis statement is hard to pluck out from the rest of the writing but the reader still somehow gets the point anyway, that is a good thesis statement.
If your later ideas aren't clear enough that you have to blatently list them at the very beginning, you obviously didn't write your paper very well. You make a valid point that it may help the teacher grade them, but again, if you can't write a clear enough thesis statement without having practically a word-for-word structure already set out for you, you're not a very good writer. All I'm saying is that a lack of the "I think this because this, this, and this" structure promotes creativity and individuality.
Also, a correction on my part; a paper with a bland thesis statement
can have voice, but then the thesis statement will be painfully out of place and the introduction will have poor flow.
