[jacques_chester]

> If you have the hardware resources, why not just scale up from the beginning on?

For most workloads it's wasteful to have max capacity provisioned at all times if you can instead provision on-demand.

This is true in general. For example, electricity supply is a mix of baseload power (cheap but only if left running constantly) and peaking (expensive but easy to turn on and off). It wouldn't be economical to have baseload capacity equal to maximum demand. Instead it is aimed at minimum demand and other sources make up the difference depending on demand.