Why have marketers been so unsuccessful at measuring the long term economic impact of brand building on the revenue trajectory of their respective companies?

Why have marketers been so unsuccessful at measuring the long term economic impact of brand building on the revenue trajectory of their respective companies? It seems that "brand" should be able to compete successfully with "performance" for incremental investment, given the difference in time horizons because "brand" can be amortized over many quarters, when performance investments have almost no shelf life?