The dream, as I see it, is that AGI could 1, automate research/engineering, such that it would be self-improving and advance technology faster and better than would happen without AGI, improving quality of life, and 2, do a significant amount of the labor, especially physical labor via robotics, that people currently do. 2 would be significant enough in scale that it reduces the amount of labor people need to do on average without lowering quality of life. The political/economic details of that are typically handwaved.

The morality of it depends on the details.