The physical miracles were used to show He had the power and authority to forgive.
Carry this a little farther...
Healing is forgiveness of sin...
Joh 9:1 And as Jesus passed by, he saw a man which was blind from his birth.
Joh 9:2 And his disciples asked him, saying, Master, who did sin, this man, or his parents, that he was born blind?
Joh 9:3 Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him.
Notice Christ did not correct them or rebuke them for attributing physical infirmity to sin, He simply stated that in this case it was for a great purpose. (has to do with Mat 13 and those who are given to understand and those who are not)
Jas 5:14 Is any sick among you? let him call for the elders of the church; and let them pray over him, anointing him with oil in the name of the Lord:
Jas 5:15 And the prayer of faith shall save the sick, and the Lord shall raise him up; and if he have committed sins, they shall be forgiven him.
Here, healing is plainly linked to forgiveness of sin.