Perphaps, but... there some dudes in Tevinter who likes to be slave.
Just because there are people who solved themselves into indentured service to become the publically-owned slaves, does not mean they did so because they were happy about it. It was more that circumstance dictated that this option was preferable to having either themselves or their families starve in poverty, such as the case with Krem's father after he was put out of business.
As we saw in Dragon Age 2, there's no such thing as happiness in slavery, only what some slaves come to accept as their lot in life.
Orana: Everything was fine before today!
Fenris: It wasn't... you just didn't know any better.
--
Hawke: I have to wonder why you stayed with Danarius as long as you did?
Fenris: You have not been a slave. A slave does not dream of freedom, or wonder at possibilities. You think only of your master's desires and what will the next hour bring. It did not occur to me that I could be anything else until I had a taste of it.
Hawke: But there are are stories of slaves rebelling all the time, they did in Kirkwall?
Fenris: The ritual that gave me my markings also stripped me of my memory. Whatever I was before, may as well have never been. Perhaps if I knew, I might have felt differently?