Because there isn't an audience
Naw seriously, there's supposedly an audience. I've seen footage of it being filmed infront of an audience. Of course they could be paid to laugh at certain times, or a laugh track could be played alongside the audience, or put in during editing. I know they did something similar at E3, where they would have fake clapping so that every game would get a round of applause even if nobody actually clapped.
I was honestly kidding Viz.
Well I'm being super srs tonight so fuck it.
They don't use Scientific related jokes, to be fair.
They do. Despite disliking the show, I have it on in the background quite a lot.