God heals people for the same reason that He does anything else. For His own glory.
Hank should of said he did not know why God heals some and not others. To say he heals some to "feel good", invites the notion that he gets some real sick so he could also "feel good". It is a road best not traveled. Like I said he should of said he did not know, and left it like that. Saying it is for "God's glory" is just like saying we do not know, for who are we to second guess his decisions. Hank by speaking for God, comes off as somewhat silly, in my opinion.