The truth is, it's all Christians, not just pastors, who are given these gifts, but there are many frauds out there using God's name to make themselves wealthy. These people set up "miraculous healings" in order to convince others they have powerful ministries.
The flip side: even those who have a clear annointing in certain areas, such as healing, can't treat God as a tap that they can turn on and off when it's convenient. It's not a power we have and control, it's a gift given by grace. We aren't some kind of modern-day Gandalf, casting mighty spells all over the place!
As for why I believe it, I've been healed, and I've been involved in the healing of others. It doesn't bother me that you'll call me a liar, or deluded, because my experience is more convincing than your opinion, especially as you have a very closed mind. I've also witnessed false healers, and know the difference.
One of the greatest problems we face today is the use of resources. If we, as a species, stewarded our resources properly, we could wipe out world poverty. That's a fact. Our governments choose not to do this. We could plough money into finding ways to cure diseases, but we prefer instead to find more efficient ways of killing potential enemies.
And we have to understand that sometimes the answer to a prayer is, "No."