Why would Elite humans desire slaves?
Human beings are the source of infinite problems.
True Elites, competent Elites, desire machines and expert software that can seamlessly replace human beings.
You left out a word.
>>Why would Elite humans desire slaves?
Slavery is economic on agricultural plantations. A small part of the property is set aside so that the slaves can grow food for themselves, as well as erect slave housing, make their own clothing, etc. This can be done when seasonal agricultural work is slack, or it can be done by slave children and women. Serfdom basically works the same way, except that the serf is bound to the land, rather than being chattel property.
Slavery is uneconomic in an urban, manufacturing setting. The factory owner does not want to supply food and other essentials for maintaining a worker when the worker is not needed. The system of hourly wages is much more economical, since the factory owner only pays hourly workers when there is work to be done. Sustenance of unneeded workers becomes a responsibility of charities or of the government.