It's likely the secure drug treatment program at CTC has done more to prevent future crime than any other crime fighting effort, but it is difficult to measure what has been prevented. Just locking addicts up does absolutely nothing to address their addiction, which they will engage in upon release along with the ancillary crimes necessary to obtain the substance they need.
Even if we legalized all the now illegal substances tomorrow - and, some do need to be legal, just as one of our most abused substances, alcohol - we would still need treatment options for some of our citizens. We have far too few of these programs now, and the elimination of one with proven positive effects make no sense. Or, at least as much sense as laying off people to grow jobs does.
If you, or the ones you love have been ravaged by addiction, having treatment available is often your best and last hope.