The simplest (and sometimes most pious) answer is, "I don't know," mixed with a bit of, "But I wish He would".

1. Richard Foster more or less suggested this in his Prayer: Finding the Heart's True Home. Foster wrote that he wished he could walk into every ICU ward and empty it. Alas, his faith may not be able to sustain such a monumental task - humility and the acknowledgement of one's lack of spiritual resources are something you don't often hear nowadays.

2. I first read about the connection between healing and faith from Philip Yancey's works. This is the idea that whenever God works in people, He wants them to be transformed wholistically, and not merely have their wounds disappear (like Wolverine?).

Last night's Bible study focused on Matthew 11, which included vs.20-30 where Jesus says, "God damn you, Korazin and Bathsaida! You shut your heart off even in the presence of God's great wonders! Go to hell!"

Miracles and wonders ultimately are about turning people towards God and embracing true humanity. Given the high likelihood (especially today?) that this might NOT happen, why would God bother?

3. And then writers like Glenn Miller alerted me to the Alice-in-Wonderland-like abnormalities our world would experience should every wound, ailment, sickness and what-not be guaranteed healing in this life.

Death from natural causes would cease - what would that do to the world's population? Care and compassionate for the 'sick and dying' would cease. What would all the doctors and nurses and hospital staff do? Would people even need to eat, if their bodies healed automatically?

In short, what kind of world would we have? And could we cope with this?

4. Finally, the question may be easily switched to, "Why doesn't God heal more?" Not everyone. Just more of the sick. Surely this won't cause the world to go topsy-turvy, surely this can encourage at least some faith, etc.

I reckon He actually wants to. But He's asking us (through every sermon, fellowship, experience, conversation, etc.): "Why can't you care more? Why doesn't the church pray, work and love harder? Why are our faiths so weak, distracted, compromised?"

In a word, why are we speculating about God when we should be suffering for others?