One particularly large client I recently dealt with was struggling to get their teams to meet their delivery commitments. It appeared that in every sprint they lost significant time to blockers, in some cases causing them to miss a commitment by as much as 50%.
This was a large project spanning multiple teams, of the order of about 800 people in total across development, test, product owners etc., with an estimated duration of more than two years. The impact of a consistent 50% delivery rate would literally break the budget, the customer, my client and probably the project.
A little analysis identified the problem to be rooted in the silos into which the teams were organised. In this instance, the silos were pretty rigid with poor communications between the teams. That lack of communication fostered an environment where blockers could emerge and live for extended periods of time.