Higher education course designers are missing the challenge to allow for synchronous interactions via audio, video, or even text.
In a 2011 article that looks at how few colleges and universities provide "real time" interaction (less than 25%), SLIDE was built on the assumption that conversation and interaction aids in the learning experience and thus the process. Of the the three types of interactions (Moore, 2009) student to content is probably given the most attention, followed by student to instructor. Student to student interaction seems to be less emphasized.
The study as discussed in the article accentuates the benefits of blended learning on both the students and the teachers. While even weekly face to face meetings provide the most benefit, even video-based interactions show positive results. Not surprisingly, it's the relationships that are establish that increase the likelihood of achieving learning objectives.
Reference
Stewart, A. R., Harlow, D. B., & DeBacco, K. (2011). Students' experience of synchronous learning in distributed environments. Distance Education, 32(3), 357-381.