LinkedIn is a professional network which primarily focuses on the careers / jobs market. In order to deliver better matches (while connecting job seekers to companies and vice versa) they always prompt for profile completeness.
Recently if you have logged into Google+, you might have noticed similar profile completeness prompt widget on the right of your main stream (refer image below).
Completing Google+ profile helps your friends, contacts, classmates easily find you as well as provide relevant profile suggestions for you.
So, next time when you enter Google+ just spend a little extra time to complete your profile and increase your visibility.