According to Chapter 17, why do people find it difficult to choose the path of salvation (Shreya) over worldly pleasures (Preya)?

Chapter 17 explains that the choice between Shreya and Preya is difficult because the two are often blended together, much like water mixed with milk. A dull-witted person, preoccupied with maintaining their body, family, wealth, and status, becomes conquered by and embraces Preya. As the chapter notes, as long as there is an obsession with worldly objects and the senses crave them, Preya will seem sweet. Even when both paths are presented and the choice is within one's control, this entanglement makes it hard to distinguish and select the righteous path. The text suggests only the courageous and wise, like a swan separating milk from water, can cling to Shreya.