Its gives you an excuse to remind someone that you exist in their friends list. Socializing/Networking is actually more important on LinkedIn than on FB, becaus

Its gives you an excuse to remind someone that you exist in their friends list. Socializing/Networking is actually more important on LinkedIn than on FB, because people usually have (or have had) social relations with FB people IRL, but on LinkedIn you need those excuses because otherwise you msotly just have business relations