SLAs apply to downtimes but also to slowdowns and unresponsive customer service.
It's unlikely that we'll ever see flawless systems, the law of physics still apply.

Also, if we give them the right tools, companies will be able to get really creative with their SLAs and introduce new use cases.
A late delivery can also be enforced with a SLA for example. You also have SLAs between teams to ensure a certain level of performance of internal operations.