[Jack Shephard]

It could be for several reasons. I could be because that was what the spirit needed to say through them. But my best guess is that since the brain is a super strong computer that it learns the tempo and sound of the tongue and the brain, IMO, can bring that out when someone is trying very hard to speak in tongues. I say this because I have been there. Sometimes I have even done it and after that thought, "That was me and not God." Perhaps in the pursuit of being or staying spiritual and fitting in that this type of thing happens.