Aimee -- my honest guess would be because following the events with Stephanie and her family, so much has been publicized in regards to the entire Nielson clan (and extended family) that it's pretty much pointless to try and keep the names a secret now.
And I'm sure somewhat like with MckMama -- who still refers to her older children (whose names can easily be found with little investigation) as Big Mac, Small Fry and MckNugget while Stellan has always been Stellan, part of why Courtney still refers to her son as "The Chief" is because he's always been known as "the chief" on her blog... so why change it now?