Sure, but you don't need the middleman. You can (and some large shops do) just publish the deals yourself. Add a /coupon/ or /voucher/ page or whatever the local term is and put your deals there. You'll rank for it, people looking for a deal will find it and use the "no shipping" or "5% off for new customers" deal you provide. Same effect, only you don't pay 1-10% to some affiliate publisher that has lots of incentive to damage your brand by advertising coupons that don't exist etc because the he only needs the click to get paid, leading to additional support and annoyed customers. I just don't see the added value that an affiliate publisher generates.

You almost never need a middleman. But companies, especially smaller ones, are limited for time and attention. Someone comes in and tells you they can do a service X for you that'll cost you Y and net you Z, Y < Z, many companies will jump at it - Y is still much less than it'd cost them to run X themselves (hiring people, figuring out how to do it effectively, etc.).

That it later turns out that the deal was bad for the company long-term - well, that's the reality of business. Plenty of dishonest and exploitative companies exist and are successful.

Sure, but freeing resources is something that I do consider a value. In this case, you still need to handle coupon codes, you need to create those coupons, you need to transmit those coupons to affiliates - the only thing you don't need to do is publish them on your own page.

It may be that some consultant talks shops into it, I just never understood what the value proposition is. "Look, just pay somebody 5% of your revenue and deal with annoyed customers instead of spending an hour on this once" doesn't sound that attractive.