In....or Out?

I'm all for having the language change as our  society evolves, but I don't understand why some changes occur with no apparent need or even a reason.  Case in point:    People, when, not feeling well, used to "call in sick" to work.  Lately, the term used is "call out sick."  I guess an argument could be made for either expression, but why the change?  Everybody knew and understood what it meant to call in sick.  Call out sick conjures up an image of someone feeling ill at home and shouting, "I'm sick!"