You're absolutely correct. About 10 years ago, Channel 4 or 5 (KFOR or KOCO, OKC, respectively) did a report about these booklets, or at least a similar idea, back when the idea had first come about, I guess.
They took 100 booklets and tried to hand them out to random panhandlers across the metro. I can't recall specific numbers, but I'm in the ballpark when I say that they reported something like less than 10% of these panhandlers accepted the booklets and of those accepted, only something like 3 or 5% of the coupons were redeemed.
It was 6. Out of 100 vouchers, 6 were actually used.