Um, you can practice for anything that involves communication or demonstrating your skills. Its just arrogant to think that you can go into an interview cold and rely on the interviewer to tease out your positive qualities. If they're a good interviewer they'll do their best to do that but its also on the interviewee to convince the interviewer that they're a good fit for the job.

I wouldn't present on a technical topic without preparation, because I'm not going to do a good job of explaining it or communicating the ideas - I'd be wasting the audiences time. Same with interviews - you need to be prepared to explain your work and put your experience in as favorable a light as possible.