High availability, deployment consistency and, if needed, ability to scale-out on demand to name a few. You can can have an all-inclusive environment for sandboxing, development or production use-cases. Easy to spin-up and tear down.

A good alternative is to use a database service and not have to worry about it at all. However if you do have to operate one, orchestration systems give you the tools to handle it properly WRT your availability and performance SLA/SLOs.