The only real SLA is the ability to vote with your feet and go to another provider that satisfies your business needs, or conversely to increase your investment with a particular cloud if you are satisfied with their performance. Providers know this, and they know that even if they wanted to, they can't capture all the possible values that are important to your particular business in numerical metrics. They also know that what is important to your business might not be important to another one, and therefore that it is hopeless to try to capture the entire gamut in a single set of metrics that are universally applicable. Any attempt would be futile, so it's best to stick to simpler metrics and let businesses and customers decide for themselves whether a given cloud meets their particular needs. SLA violation penalties hurt a little, but the real pain comes when you lose business.