Scope creep is the most common reason agency engagements lose money. Each individual ask is small ("can you also do a LinkedIn version?", "one more round of revisions please") but over a quarter they compound into hundreds of unpaid hours.
For agencies, the cure is not saying no — clients ask for what they need. The cure is converting every out-of-scope ask into either an explicit change order with a price, or an explicit goodwill note that surfaces the value being given away. Both protect the relationship; silent absorption damages both.
Track scope creep visibly: tag each task in time tracking as "in scope" or "out of scope", and review the ratio weekly. The number itself is the early-warning signal — by the time a project is over budget, it is too late.