The Calling Card List is usually not required for searching for yourself (i.e., it is quicker to get your Profile via the pie menu and you cannot IM yourself), but it would be very useful for group land management. If your own card was automatically placed at the top of the list then you could easily select yourself as the avatar to sell the land to (for transferring land from one group to another).
Original Description that the first two comments relate to follows:.
When transferring from one group to another (esp when nearing tier limit and adding group tier might trigger a price increase) it is common to sell land to yourself of 0L$. However, the only way to do this is to search for your name, while I can select others via Calling Card. I have a premium account called Jenn Masala and had two non-premium accounts. On searching for Jenn Masala I found a Jenna Masala. There was too much risk of clicking the wrong name so I upgraded one of the alts to premium, even though Jenn Masala was only a few months into an annual contract. I would not have needed to do this if I could have selected Sell to Self.