Culture U has this right: The Four Roots of Engagement
#1: People Want to Be a Part of Something Bigger Than Themselves
#2: People Want to Feel a Sense of Belonging
#3: People Want to Go on a Meaningful Journey
#4: People want to Know Their Contributions Make an Impact

What are you doing to engage employees?
http://www.cultureuniversity.com/the-four-roots-of-engagement