Understanding a well-written abstraction in code is similar to understanding a simple flow chart. Just as you don't need to understand every interconnect and resistor value when observing a flowchart (versus a schematic), reading through a well-commented header file of an abstraction provides nearly all of the information required to use any of the underlying implementations. There is no need to get buried under the details and idiosyncrasies of each implementation.

This limited bird's-eye view means that future developers are more likely to consume the code since it is presented in a well-defined, well-documented, and consistent manner. The overall knowledge and time required to grasp an abstraction is much less than that required if implementing the same functionality from scratch.