Though many slaves were originally used for labor, to remain profitable the cost of the slave, the collar and the tax, fees, bonding ritual and cypher storage (one time) fee would have to be worked off and because slaves were hard to come by as well the typical slave was expensive and thereby took several decades to turn a profit, remember, they needed to be fed and housed as well.
So legal slave ownership was relegated to the upper class and few large scale plantations in unincorporated areas or small settlements in the unprotected lands.
It was a rare sight to see one with a commoner but not unheard of, typically an older man who'd lost his wife and children or never been married and saved his excess, living frugally, working in a skilled profession could manage it later in his/her life. Those would have the simplest collar and would generally hide it under a scarf or collared shirt.
Being so precious and rare, slaves were treated surprisingly well. Though the initial acquisition was often dramatic and traumatic, the life of a modern slave, off plantation, was considered even enviable. Though there were always exceptions, the rule was they are treated like living jewels, owned yes, but shown off, appreciated and well taken care of.
In a way they had more power over their owners than the reciprocal. They represented a sizeable investment even for a noble. The mark of a good slave was desired above all like a gem of high quality, thereby one who shown brightest was one who was adored, respected and treated like royalty.
They needed to be vibrant, alluring, entertaining, educated, charming, beautiful inside and out and of course loyal and obedient, only one or two of those can be reasonably achieved by force, the others need to be cultivated by a doting and careful master and the hired staff. That was the true test of nobility, the height of noble society. Owning many slaves was only possible by the uber rich, royalty, or illegal means. Those illigitimare owners were marked for death and justified so. Their bounties were often higher than thieves and murders. So too were kidnappers.
Not everyone could own a slave properly, the energy and time required to form a trusting relationship was akin to marriage, or not unlike having a tulpa. We require a lot of attention to be vibrant and expressive. A lot of patience and a lot of doting.
So though slaves were often seen as the three beastkin, entrapped or taken against their will; without their choice to be loyal and willing to serve in exchange for a good life, they were beyond useless and undesirable. Though such slaves were still not tossed aside, there were no refunds, no, they were trained properly, as long as it took, talked to by other "sister and brother" slaves, and given the choice, coaxed, or effectively courted.
