I would think that two of the imperatives are the most important. Those are the economic imperative and the self-awareness imperative.
The economic imperative is the more practical one. As we all know, the world's economy is becoming more and more globalized and intereconnected. It is very likely that people who are starting careers today will have to interact with people from around the world in their business careers. For this reason, it is important for them to be able to deal well with people from other cultures.
The self-awareness imperative has more to do with personal growth. I grew up as an American living in a foreign country. Therefore, I was forced to live intercultural communication. I feel that this has made me understand myself and other people better. This has enriched my life and seems to me to be a good reason (though it carries no clear economic benefits) for studying intercultural communication.