In the latest Manga we have seen Madara's "indifference/carelessness" toward Sasuke.
Many probably think that Madara has dismissed him that he viewed Sasuke as nothing that could be useful to his cause. This is a fallacy Madara had a very specific objective in piercing Sasuke's heart.
His lecture while Sasuke lies dieing on the ground simply emphasizes this:
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Here Madara reveals his intentions and his greater knowledge of the Sharingan. He eludes to the fact that Sasuke is still holding onto a better future. This is the key to awakening the Rinnegan.
The Rinnegan by its very nature is Samsara the wheel of suffering. It is never ending and all consuming. One who awakens the Rinnegan has no hope for the future and can only perceive a never ending cycle of pain and suffering, that is the emotional trigger. Aka this state is personified by Madara.
Madara is trying to give Sasuke a chance to come over to his way of thinking and awaken the Rinnegan at the same time.
Eg in order to awaken to Rinnegan Sasuke must let go of Itachi's legacy and concede that the world is not worth saving.