There are plenty of large databases of image, video and audio material of private individuals tied to their identity. Youtube, instagram, Facebook, LinkedIn etc, all of these give you access to extremely high quality material as well as a lot of context that you could use to make a deepfake more believable. And that's before we get into non-public accessible databases, of which there are plenty.
Yes. Several years ago when banks started using voice pattern recognition as part of telephone banking authentication that was a pretty cool advance, but now it's looking redundant.