One can indeed say that a business truly grows when its customer base grows as well. For example, if you have an auto garage in a certain neighbourhood, then your initial customers will only be those who reside in the particular locality. However, with time, as your customers grow in number (given the fact that you provide them with the best customer experience), the recognition of your garage beyond the neighbourhood also grows as both are directly linked. This helps in building credibility and trust while tapping into new target groups which will have more potential customers.
In simple terms, customer retention is like growing your network. It constantly keeps you on your toes and helps motivate you into constantly improving your offerings, adding it as a major source of business growth.