I've asked some professors this questions and none of them have seemed to been able to give an answer that didn't lead to both them and me having more questions.
To put into context:
I have my B.S in Marketing and have been working in the marketing industry for just under 4 years. Of all the jobs I have had and been interviewed for having a strong knowledge of SEO (Search Engine Optimization) was required to even be considered. In order to market using anything digitally based you need to understand SEO and in some cases ASO.
Never in any of my textbooks was SEO talked about even though it's not a new topic and my textbooks were 2011-2013 publications. SEO was mentioned but never talked in a sense of someone would know what it is and how to use it.
For a concept so important in the marketing industry today why don't textbooks talk about it? I've looked through half a dozen of my marketing books and I've even asked to look through the new 2015 editions my professors were given.
Are their limitations to what goes into a textbook? This sounds silly even to me but anyone who works in marketing knows how important SEO is and when a textbook is written by people who have worked in the marketing field it only makes sense that they would want to include to most important industry topics to-date so that a new 2015 textbook doesn't seem outdated.