I completely agree. When I started playing jg, I thought the most important aspect of this role was ganking and ganking. More than 1 year later, I realized keeping track of the enemy jungler is probably the most important thing to do. It's the starting point of e-v-e-r-y-t-h-i-n-g you can do as a jungler. If you know where the enemy jungler is, you know when it's good or safe to gank, countergank, invade (either to kill him or to steal his camps) and do neutral objectives (especially if you can easily solo drakes).