A lot of analytics funnels do this. You don't always want to just track sales in a funnel. You want to track how many downloaded but don't sign up (acquisition

A lot of analytics funnels do this. You don't always want to just track sales in a funnel. You want to track how many downloaded but don't sign up (acquisition vs activation). Or signing up and logging in vs what they call a golden moment. Also there's a reason people pay for referring a friend - it's easy to track who cares enough that they'd tell friends.