What is the "sin" (ithm) that is present in gambling (maysir)?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It distracts from the remembrance of Allah and from prayer, and it causes enmity. [Ibn ʿAbbās]
2. It leads to injustice and withholding of rights. [Al-Suddī]