These systems are not typically designed to protect individual privacy, but since these services are typically free there is a strong economic drive for the service providers to harvest at least some information about their user's activities on the site in order to sell that information to advertisers for directed marketing.
Although I have studied the following definitions, I am wondering if the following definitions related to the bold part, and I cannot yet get what is the concept of the bold part yet.
Macmillan: economy drive
Cambridge Business English Dictionary: economy drive
Thanks in advance