Agencies do not lose pitches, they lose follow-ups
Ask a studio founder why a proposal went cold and the honest answer is usually that nobody followed up. The deck was good. The price was reasonable. The client went into a budget cycle, three weeks passed, the agency assumed silence meant no, and by the time anyone thought about it the project had been given to whoever called.
This is a structural problem, not a discipline problem. In a small agency the person writing the proposal is also the person shipping last month's project, and delivery always shouts louder than business development. The only reliable fix is to move follow-up out of memory and into a system that surfaces the proposal that has been silent for nine days.