Because virtually everyone tests these things with two languages they're familiar with, else you couldn't really verify if it was correct or not. For languages you're not familiar with, you don't have the "mental mode" to talk using a translator, that is there is more to this than just "talking", there is cultural norms, local dialects, slangs etc which are to be respected when learning and speaking languages with native speakers. When a person who speaks English and Italian tests these things. They know what they're in for an compensate a bit.
Google translate screws up for me really, really hard sometimes when I'm speaking Korean but I'm already a pretty strong speaker, native so I know how to work with the screw ups...and laugh about the really bad ones. I'm not going to go into a meeting and blast off with an auto-translator without understanding what I'm saying or have someone to make sure I'm saying the right thing by talking with them first.
I personally wouldn't feel comfortable using something like this for anything of real significance, a really good translator can ensure the message gets delivered.
