"The man had a choice to be healed or not. There had to be a 'want to' in his will. He could have decided to stay unhealed forever, and there could have been some reasons to do so. He may have wanted to remain unhealed so he could just lie around, or he may have grown accustomed to begging and knew begging was easier if he had a severe health problem. He may have become comfortable in his role as an outcast. He may have used his illness to disconnect from the world and the other pressures of life. There are many reasons that he may not have wanted to be healed, even though Jesus was offering to heal him. Jesus took the time to ask if he wanted to be healed, rather than just barge in and heal him on the spot."
Source: Stephen Arterburn, Healing is a Choice, p. 19.