Not many people are disputing that. But the existence of miracles is a far cry from the universal supply of miracles on demand.
If it is always God's will to heal why are some people not healed? Why do we get sick at all? If God was going to heal everybody on demand, wouldn't it make more sense to simply eradicate sickness among his people? Otherwise it makes God look like some kind of bumbling half-wit who needs to be prodded and cajoled before giving a "ah, sorry, I'll get right on it" kind of response.