Here is a prior discussion that addresses the topic of CC/BCC and email:
http://smnetwork.org/forum/tools-of-the-trade/email-best-practices-for-teams/Regarding what your team has been doing, have you sat down and clearly reviewed with them what your expected protocols are supposed to be? Do they know what CC and BCC do, both on the sender & recipient/respondent sides? In my current job, a "timely manner" for an email response is 30 minutes, tweets 5 minutes, text messages 2 minutes. How about you?
It's taken for granted that people know how to email and correspond promptly. However it is critical to realize that especially with younger SMs, we're in the post-email generation. Many of them have very little practice in email, and next to none of it in a business situation. I never had training in email, correspondence, timeframe of reply, etc when I was in college 15 years ago because the students were leaps and bounds ahead of the faculty when it came to technology. Average typing speed nationwide is still around 40WPM. For the younger generations it's actually dropping, as they do more typing on touchscreens than on keyboards. Business-appropriate writing in general is not taught much in arts curricula. Some uni students will learn academic writing but it isn't quite the same. SMNetwork mandates business-style writing and proper grammar, and we can see how well that works out.
If the only thing an intern learns to do over the course of an internship is the method of sending a proper email, then I'd say the internship is 100% worthwhile.