Why the Bible emphasizes "the iniquity of the Amorites" and not of the other tribes?

In the Bible, the phrase "the iniquity of the Amorites" is used several times to describe the sins and wickedness of the people who lived in the land of Canaan. This phrase is often emphasized above the sins of other tribes, such as the Hittites, Perizzites, and Jebusites.