Primarily because their mechanisms of action are easier to study in vivo. Sentience is a red herring. I addressed this in https://news.ycombinator.com/item?id=

Primarily because their mechanisms of action are easier to study in vivo. Sentience is a red herring. I addressed this in https://news.ycombinator.com/item?id=18000854 https://news.ycombinator.com/item?id=18000854