Do you have an SLA in your contracts as standard ?

SLAs are useful when there are different level of service that can be provided. salesforce does not offer different levels of uptime and performance based on a contract. All customers, large and small, get the best performance, and the best security. Additionally, if you experience some kind of service issue (historical uptime is above ~99.95), there are thousands of other customers experiencing the same issue, and you have the collective force of all of your discontent and pending renewals that puts pressure on the engineering team at salesforce to be the best.