I feel this is because of the education I have received, or rather, not received. Many of my college Spanish classes have been teacher centered. Although we hear Spanish the entire hour, I feel we have little opportunity to work on our speaking skills. I don't feel this has prepared me enough to teach in the target language. I think it is the teacher's responsibility to expose the students to the foreign language as much as possible from the very beginning, but I wonder how many first year teachers are really prepared for this.
Communicative competence covers a broad range of elements.
I think the university should better prepare foreign language teachers by including more speaking classes. So, yes, I think foreign language teachers have a responsibility to be communicatively competent, but many fall short of this. I have been studying German for almost 10 years now including a year at a university in Germany. Even that is not enough though, because there will always be those off the wall vocabulary and grammar questions that even the most prepared teachers are not ready for. In order to reassure my self in times like these, I like to remind myself that I am not an expert, and I want my students to know that.