A reason for using the contribution$-$margin approach in a marketing cost analysis is that:

It tells management which territories or products are profitable.

Arbitrarily allocating indirect expenses to individual territories or products can give misleading information to management.

Ledger costs can be allocated into activity groups.

Each marketing unit $($product$,$ territory, for example$)$ should bear its full share of costs.

This approach is especially useful as a basis for long$-$range planning.