They were discouraged because the law at that time stated that their earning basically belonged to their spouse, and also they couldn't own property, so they couldn't use their money in any way other than giving it to their husband. With this kind of a law, nobody would work.
The Indian Appropiation Act contained several acts enacted by the US Congress between the late 19th century and the early 20th century.
One of the most outstanding acts was the Indian Appropriations Act from 1871. According to it, Indians would not be treated anymore as an "independent nation, tribe, or power". In turn, Indians would be considered as "wards" of the federal goverment. This provision considers Indians somehow like children, as if they needed a tutor.
From this moment onwards, the US goverment did not have to mantain endless negotiations to sign treaties with the different Indian tribes. Also treaties that had been signed before the Act were not enforceable anymore.
The act made much easier for the US government to exercise control over lands which were previously dominated by the Indians.
