Self-efficacy is not the same thing as confidence. Confidence is often equated with arrogance or hubris and may have little relation to actual ability. Self-efficacy on the other hand is based on real factors. The primary sources of self-efficacy are actual performance experience, comparisons with and observations of the performances of others, what others say about your performance, and your general physical well-being at the moment. So, for example, say that you are a runner. Your running self-efficacy will be determined by how well you have run in similar situations in the past, how your running compares with other runners, the feedback you have received about your running, and your general sense of well-being and preparedness for the challenge at the time. Self-efficacy is a much more informed self-evaluation than confidence and that is why self-efficacy is important to performance.
This sense of informed self-evaluation is also why I believe writing self-efficacy plays an important role in transfer. It is a key part of self-knowledge that will help continue growth and development long after students have left the classroom. Writing self-efficacy is not the same thing as the first-semester student who tells me she got all A's in high school English or that his mom thinks he is a good writer. I can't tell my students they are great and see their writing self-efficacy increase. In order for my students to gain writing self-efficacy they need the opportunity to perform -- they need to write -- hopefully giving both deep and broad experiences, but they also need the opportunity to compare their performance, their writing, to that of others which then helps them judge the quality of the feedback they receive from others about their writing.
I don't want to simply go through the motion of preparing my students for their future writing challenges -- I want to increase their own sense of preparedness and their sense of writing self-efficacy.