The problem
Following up consistently is one of the hardest things to do manually. You send a first email. You mean to follow up a week later. Something comes up. Two weeks pass. By then it feels awkward to reach out again so you move on.
Most leads are not lost because they were not interested. They are lost because the follow-up never happened.
Tracking this manually in a spreadsheet does not work either. You spend time checking when the last email was sent, deciding whether to follow up, and writing the next message. For a small team or a founder doing their own outreach, this discipline is almost impossible to maintain consistently.