A client's intern asked me in the elevator why we track billable time at all, and I had no good answer
She said her old agency just billed a $4,500 retainer and never looked at hours, so I went back to my desk and counted 12 timesheets we chased that month for projects we'd already finished.
The retainer model doesn't mean hours get ignored, it usually means there's a cap built into the fee and the agency tracks hours to make sure they don't blow past it. A flat $4,500 can quietly become a loss if nobody watches the clock. Chasing 12 timesheets for finished work sounds more like a process problem than proof that tracking itself is pointless.