A video editor "mixed" this promo for Saturday Night Live. How can you tell? Because the mic for the guy on the left is in the left channel. The mic for the guy on the right is in the right channel. Just like the way it was recorded into the camera.
The production mixer (they're not really called that in TV -- I don't know how SNL does it but the position is likely called the "A1") is the person who was responsible for recording the dialog. And if you have two people, like this, you slap a lavaliere mic on each of 'em and send the mics to separate channels.
Very pro. That is, in fact, the pro way to do it.
But that's assuming that the person who will be touching the audio last (meaning, before it goes out to air) knows what they're doing with audio. And if you have a picture editor working on it, then it's likely they don't. Have pity on them. They're just simple picture editors. They don't know any better.
In Final Cut Pro the tracks that the two channels of camera audio would be dragged onto are, by default, panned hard left and right. But do you really want Bill panned hard left and Steve panned hard right? No, of course not. you want them both in the middle.
You can even hear Bill switch channels as he turns toward Steve. That's because as he turns toward Steve he's talking into Steve's mic. And he ends up (momentarily) being louder in Steve's mic than his own.
As the job of assembling all these takes and then putting them up on Hulu is probably one of the lowest-priority edit jobs on the show, it's probably thrown at the lowest-level editor they've got. Heck, the producers may have even lied to the editor and told 'em that someone was going to actually do the audio mix so they "don't have to worry about it". But the fact is, that as long as the audio seemed minimally acceptable to whomever uploaded it, that was the end of caring about it.
The trouble you get into when you do something like this is when somebody watches the dang video with (say) a speaker unplugged. If that happens then you lose one of the hosts. Either Bill or Steve will sound distant (because you'll only hear their feed from the other guy's mic.)
And mixing in FCP is no picnic. But it can be done. You just need to pay attention to what audio is bussed where.