Water is a visible content. You can see the quantity of water. It can be a glass of water or it can be a tank full of water. If it is a glass of water, you can charge it in a few rotations but if it is a tank of water you will make 100 (approx) rotations to charge it. Because it is visible content, we know how many rotations will be needed to charge it.
But a goal like healing a headache is not visible. We cannot know in how many rotations we will be fine. It is an invisible goal. If VK can send energy for 30 minutes on its own then you are free, you can do any other job.
Another example is a student who has to score better marks in exams. It is a goal that needs much energy (but you don’t know how much, you keep sending the energy). But, will you keep sitting and sending energy till their exams are over? what about the next set of exams? there are many exams in a student’s life, right?
what if VK can keep sending energy automatically? Yes, VK sends energy for 30 minutes automatically on its own. It is designed to do so.
this makes your life easy and simple
A "direct request", energy through the "Photo method" needs a request to VK again and again. To make it simple, VK can keep sending energy for 30 minutes.
To make it more simple, charge water with the required energy and give it to the student to keep drinking for all the exams in his entire school time. You are more free 