Promotional diaries are most useful to companies targeting the young market, most specifically females in the said population. Say, a company that sells clothing to female teens of age 10 and above. What appeals more to these people are fancy things and a diary is just one of them. Distributing promotional diaries to this market creates an area of influence that extends to convincing it to prefer the brand being promoted. Again, the company need not distribute clothing samples for free, as such approach requires excessive amounts in the inventory and of course, a lot of expenses. Promotional diaries can be of great help. These items serve to appeal to the market and persuade them while the item is in use.
Non-profit organizations may distribute promotional diaries, too. After all, the aim is to create an attachment in usage and help the brand or idea grow in the society.