Under pressure to consolidate resources, usually driven by management and especially regarding processor capacity, there is often an urge to "use up" any idle processor cycles. Idle processor capacity tends to be viewed like it's whitespace on a written page—just begging to be filled up.
The logical equivalent of filling up the "whitespace" is absorbing idle processor capacity by migrating applications that are currently running on other servers and turning those excess servers off or using them for something else.