Because most agencies bill for effort, not outcomes, so there is nothing concrete to check. If you cannot see what you paid for, it is worth finding out why.
Signals
Straight answers to the questions business owners actually ask about marketing and the agencies they hire. One question. One or two sentences. If that is not enough to answer it, we are not doing our job.
You should not, unless it shows what changed in your business since the last one. A report that only shows activity is a report about the agency, not about you.