If God gave us freedom, and He doesn't directly intervene with what is going on here on Earth, then what's the use of prayers? What's the use of asking God to make the storm miss our place, to stop the volcano from spewing out lava and ashes, and to make our work better and more tolerable?

Here's a bit of statistics:

There are 6.93 billion people around the world. Even if only 10% of this number prays and asks for less calamity and hardships, it is still a whopping 693 million individual persons praying to one God (with different names) for one single thing: world peace.

So the question remains: with God's omnipotence and immeasurable mercy, why do the following, among others, still exist:

It is estimated that globally, there are 16 million thunderstorms each year.
About 50-60 volcanoes erupt every year. 20-30 are effusive (lava flows), another 20-30 are explosive.
Out of 2,207 work-related suicides in 2007 (in Japan), the most common reason (672 suicides) was overwork.

This has been one of the most persistent question (along with a lot others, which makes other people think of me as an atheist)  that I have for a long time now. And finally, after having a lot of "spiritual" conversation with my kambal, I think I finally have an answer.

When we pray, God does not change the world and the people around us. Rather, we "activate" the God within us which let us see the people, things, and events around us in a different perspective. This also gives us the divine wisdom to understand what is happening and the divine strength to do the right thing. Therefore, praying is not about changing something or someone around us. It is simply changing ourselves to be able to participate in God's creation in a God-ly way.