I like this too, but unfortunately some groups just don't want to take it, especially if they're accustomed to RPGs (like high fantasy) where failure just isn't an option, because failure means that the big bad evil guy wrecks the world. Some players get so that they won't accept anything less than total victory.
I ran into it last session, when the PCs were trying to foil an assassination attempt. It was a tough fight against smart, well-equipped foes, but eventually they knocked out half of the enemy. The wetwork team knew that if they pressed the fight, they would probably start suffering fatal casualties, so they broke off the fight and offered to negotiate. They were quite willing to slink off with their tails between their legs.
The PCs insisted on unconditional surrender. They weren't content to simply fulfill their mission; they wanted the other team's gear so badly that they were willing to fight to the death for it. Luckily for them, the other team had the sense to slip away unnoticed while the PCs were making their demands. They were bummed that they couldn't make pickup on their fallen allies, but at least they didn't need to deal with the greedy, bloodthirsty PCs.