Why so secret?

I recently read an interesting article about 10 restaurants (all of them fast-food based) that talked about all the hidden or "secret" items on their menus. I thought it was interesting that restaurants would go out of their way to hide things by not putting them on the menu but still be willing to sell them. These restaurants ranged from Starbucks to Subway and included everything in between.

 

Personally, I think putting more items on your menu could bring in more customers because it gives you more of a variety of choices. My favorite example is Jamba Juice. What if you get there, but then realize you aren't in the mood for a fruity smoothy? No worries. You can just order a candy-based smoothy!! I love Jamba Juice, but I never would have thought that they sold candy-based smoothies because it's never on the menu and it screams fruit smoothies to me, but who knows?? Another restaurant that I found particularly interesting was Popeye's. Ever heard of 'naked chicken'? I didn't think so... but it exists, so next time you are feeling like unbreaded Popeye's chicken go ahead and ask.

I suppose I can understand taking something off the menu if it unhealthy, but if it's something you aren't proud of offering then why not get rid of it altogether? Why do restaurants even hide items in the first place?