Here's why:

* Pedigrees track inheritance within a family: They show the relationships between individuals and how traits are passed down across generations. This is primarily used in genetics and medical fields to study inherited diseases and traits.

* Cladograms depict evolutionary relationships: They are tree-like diagrams that show the evolutionary history of organisms, grouping them based on shared derived characteristics (synapomorphies). These characteristics are usually anatomical, physiological, or molecular.

Instead of pedigrees, biologists use various data sources for creating cladograms:

* Fossil records: Provide information about extinct organisms and their evolutionary relationships.

* Anatomical and morphological features: Comparing physical characteristics like bone structure, organs, and body plans.

* Molecular data: Analyzing DNA and protein sequences to identify similarities and differences among organisms.

In summary: Pedigrees focus on familial relationships and inheritance patterns within a species, while cladograms focus on evolutionary relationships between different species across broader timescales.