I'm sure we could go deep into rehab and how it's a net-good for society, but given your comments so far, I feel it would be a lot like preaching to the choir.

Rehab in all forms is good, whether physical rehabilitation, mental, or medical/drug related.

More healthy people in society means a more productive society. Period. Charging people out the ass to simply live and exist without constant discomfort is detrimental to the productivity of our society at large. Rehab is one tool to help society obtain and maintain a high level of productivity continually.

There's obviously more to the discussion of productivity but it kind of falls outside the context of the discussion.