This is true if you are building your own start-up from the ground up. It is also relevant if you work with a company instead of for a company.
A good example is when I worked with Britam. I was responsible for fetching my own clients... and Britam provided us with a professional email and branded street activation merchandise, like a banner.
Every time I signed a new policy, the client data that I created became Britam's... The data was mine and not Britam's, which is why we were expected to look for our own clients. In this case, cold calling is a vital strategy to use to build your own database from scratch.