Use SCC detection when the problem involves:
Directed graphs with cycles that you need to compress or simplify.
Finding groups of mutually reachable nodes.
Compressing a directed graph into a DAG for further processing (DP, topological sort).
-SAT problems or dependency analysis (circular dependencies).
If your graph is already a DAG or is undirected, you probably do not need SCC detection. Use topological sort for DAGs and connected component detection for undirected graphs.