Final answer:
The Sioux did not accept the Dawes Act because it broke up their tribal identity and threatened their way of life. The act's allocation of land resulted in the loss of Native American land to Anglo settlers.
Step-by-step explanation:
The reason the Sioux did not accept the Dawes Act was because it broke up their tribal identity.
From the native perspective, the Dawes Act was seen as the final assault on their way of life. Dividing the land into individual allotments prevented them from hunting and ended their communal lifestyle, which was the basis of their social, economic, and religious ways of life. The allocation of land conveniently resulted in millions of acres of 'surplus' land, which the federal government could redistribute to Anglo settlers, leading to the loss of even more Native American land.
This resistance to the Dawes Act was not unique to the Sioux tribe; many tribes saw the act as a threat to their culture and sovereignty, which is why they opposed it.