RE: Knock, knock - Can I come in? San People of South Africa Issue Code of Ethics for Researchers
It really is best practice, but usually is up to the researcher whether they will include it in their study. Even with this code of ethics, it is not set in law, it is simple voluntary etiquette and show of respect. Any sort of consultation is difficult and time-consuming, and certainly if we are talking about students it really may be quite intimidating! Often it may have to be done via a translator and in a completely foreign culture with foreign social etiquette and foreign power structures that need to be acknowledged. As a student, the thought of standign in front of a bunch of people and talking may already be scary! It's not easy. But it is the most correct way to do things if you want to be fully respectful to the study population.
As this article notes, the San are the first tribe in Africa to release their own code of ethics, so that leaves a lot of tribes where the ethics is still primarily guided by the anthropological (and other research areas) communities themselves.
I speak in front of a lot of people almost every day, if today the thing flows normally, when I started to do it ... I trembled on all sides and sweated through every pore, and spoke to people of my culture and customs . I can't imagine how I would feel to speak to people who have a culture and customs completely different from mine, being afraid of being impolite.
To blur these differences it is really there to have a code of ethics.
In all fairness, by the time someone gets to the end of a study they should feel a lot more at ease with the study population (although it of course depends on the nature of the research). I think the initial presentations and introductions are more likely to create presentation sweats!