That's consistent with my own experience at Google. It's not that working on improving a thing isn't rewarded, but it's just much easier to demonstrate impact when you can use the word "launched" in your self-assessment Launching is in itself an accomplishment, while optimizing requires you to also collect data, do analysis on the data, and show a positive impact. "Impact" here is one of the buzzword categories that goes into an assessment of your performance as an employee.