Because follow-up has no scheduled time. It is urgent for no one, there is no customer asking for it, and it lands on Friday afternoon on the desk of the person who has already priced twelve inquiries that week.
Three causes recur, and they are not solved in the same way. The first is tracking: on a Tuesday morning, no one can say which quotes have been waiting for a response for more than fifteen days. The information exists, scattered across email, management software, and a spreadsheet. The second is discomfort: following up feels pushy, especially when there is nothing new to say. The third is content: a follow-up that says “I am following up with you” gives the customer nothing, and the person writing it knows that.
Follow-up software solves the first problem. It solves neither the second nor the third, and that, in our view, is why many installed tools eventually stop being used.