The total cluster load is low.
When the total cluster load is low, DRS does not power off the host.
The following are possible reasons why DRS does not power off the host:
Distributed Power Management (DPM) detected better candidates to power off.
vSphere HA needs extra capacity for failover.
The load is not low enough to trigger the host to power off.
DPM projects that the load will increase.
DPM is not enabled for the host.
DPM threshold is set too high.
While DPM is enabled for the host, no suitable power-on mechanism is present for the host.
DRS cannot evacuate the host.
The DRS migration threshold is at the highest setting and only performs mandatory moves.
Address the issue that is preventing DRS from powering off the host.