Character properties describe state. Relationships describe connections. Arc points describe change.
A character card is useful only when it helps the text
Names, traits and notes matter when they prevent inconsistency or support decisions. The stronger value comes from connecting the character to actual scenes and sections instead of keeping a detached biography.
Relationships deserve their own structure
Many stories move because relationships change: trust becomes suspicion, dependence becomes independence, rivalry becomes alliance. A list of characters cannot express that by itself.
Arc points make change inspectable
An arc point ties an important shift to a place in the manuscript: a decision, loss, reversal, realization or broken relationship. That makes it possible to inspect whether the change is earned and distributed across the story.
When this is overkill
A short essay, simple story or early draft may not need any of it. Add character structure when memory stops being enough or revision starts asking cross-manuscript questions.