These days, more suppliers are stepping up to meaningful service-level commitments, but the customer has to establish significant negotiating power to gain those concessions. If the supplier still balks at remedies after you've led him down this logical path, maybe you should ask yourself if you've selected the right supplier. Only, do it out loud in earshot of suppliers. It tends to have a powerful effect on them. Sometimes you can even see them sweat and squirm.
Chances are, it's considered a necessary evil, at least from a budget or process standpoint.
Additionally, competent IT procurement can win performance assurances, customer rights and remedies and flexibility from suppliers. But like anyone else, your procurement team needs to be motivated and supported. They must be given the authority to conduct negotiations with suppliers, just like military leaders need the authority to conduct wars like warriors. Like anyone else, accountability and visibility get results. If they're aware their performance will be judged based on savings, reduced risk and how well the deal works, their incentive to make the best possible deal increases.