Probably because you're not used to (hearing the presented foreign languages).
Same as english (both UK and USA I guess) was instantly categorized as "synthesised", I had exactly the same thought about french version. Moreover, the female voice does not articulate well enough (at least for the text they choose) and even as a french-man myself, I had a hard time guessing what she was actually saying for 2 words. She had also some weird intonation...
About russian side, it sounded more "chopped" than other languages somehow. Though i can't say I speak it
Best choice IMO. There's a reason not everybody's a singer ... and that commercial adds choose specific voices according to the emotions / stimulii they want you to feel.
Though I would love to get my hands on the same kind of AI as Kane acquired (yet rather creepy if you remember the whole stroy), we're still miles from anything close to that.
Your proposition is a very good one, but not feasible with actual tech. Or not without a huge portion of players making fun / being irritated by the chopped "one-tone" voice currently on the market.