some one without a hand or leg should ask him to magically grow one
There're laws of nature set by God. Studying and understanding these, miracles are actually performed but not seen as miracles, just as science.
The vital organs of the human body are all concentrated in the head and torso. A human (or any animal) could lose any or all limbs and yet survive. In case of poisonous bite or gangrene, even amputating the limb to survive. Just like adult teeth, if lost, will never grow again, so are the limbs. However, there're dentures and prosthetic limbs to replace them.
Praying to God to grow new tooth or limb by the flesh is against God's law of nature. Finding out ways to fix it (as with the invention of dentures and prosthetics) is the way God meant it to be. Blaming God for illnesses or accidents causing loss of limbs is also against God's law of nature, which includes synchronicity and you can't always get what you want.
An illustration. Drunk and speed driving, nevermind. If you crash and lose some limbs, just pray to God to grow them back. Smoke, drink and eat to your heart's content and got cancer or whatever, nevermind, just pray to God to heal you. Even without any religion, human commonsense and conscience will tell you that the world doesn't work that way.
Without synchronicity and if everyone always get what they want, there'd be no human society as we know it today. All'd be happy robots.
What's synchronicity? Simple put, events and incidents that happen to you don't involve you or your action only. They involve chains of events and incidents happening to others and actions of others linking up to you. To others, your actions are part of the links to their synchroncity too.