Jesus had healed them and they were no longer blind. They couldn't see, either, but they were healed. We pray with full counsel of God in mind. We have a taste of God's promises, not the totality. If Christians were not to be sick, we would not die.
Death is the ultimate sickness, and sign of the curse.
All Christians still die, at least until the Rapture. Prophet Elisha performed many miraculous healings. He even raised the dead. Yet he died from an illness. The apostle Paul practiced healing.