While I am not too sure about the example used in first para but it's quite a good read on acquisition vs retention of users. Also, do give a try to the model mentioned in the last para. Quite interesting it is.
If you develop a great product like Uber, there’s some percentage of cohorts that use your product forever. They’re addicted to it. Even if they stop using it at some point, they come back. Facebook would have a hard time growing to 1.6 billion monthly active users if a lot of people used it once or twice and then never used it again.
Image Credit: https://medium.com/@danwolch
Let’s see what happens to your growth if you weren’t like Facebook, and you didn’t hang onto your cohorts for a long time like Facebook. Let’s say you continue to have 1,000 people sign up every month, but over time those people end up quitting your product. This is what the chart looks like past 2016:
By the end of 2018, you’ll only have 13,000 users of your product. You had 11,700 people at the end of 2017! Even though you grew 700% in 2016, you only grew 11% in 2018. The rate at which you’re growing is slowing significantly, even though you continue to add 1,000 users a month. You can see this visually in the bottom right of the chart, where all of the cohorts seem to stack on top of one another, but don’t add up to anything. You can’t even tell the cohorts apart, they just look like a colorful set of stripes. By the end of 2018, the new people you’re adding every month are barely replacing the people who abandon your product from all of your previous cohorts.
Read the full post at - https://medium.com/@danwolch/good-vs-bad-retention-the-user-and-revenue-impact-4edc02e48930#.34blee3w3