2 Big Reasons: 

1. The right roles have not been defined.  Phil Harrel, VP Corporate Sales, asks, "The way your buyers purchase products today is fundamentally different than it was 10 years ago.  Has your marketing playbook changed as well, or does it look very similar to how it did 10 years ago?" 
2. Resources aren't invested in the right spots. Wordstream reports, "Outbound marketing is harder to track and less profitable than inbound marketing, yet ironically, organizations still spend as much as 90% of their marketing budgets on outbound marketing."

Read other reasons in this ebook or slideshare presentation.