A laugh track tells an empty room that other people have already approved the joke.

Manufactured approval arrives before your own reaction can form. The sound tells you that this was funny, that others already agreed, and it works because we are heavily influenced by what appears to be the consensus of a group. Judgement is social even when the group is a recording.

Watch for the same effect in ordinary settings. The already-high number of approvals on something, the room that has clearly decided, the colleague who tells you what everyone thinks. Ask what you would have made of it with no signal about others, and notice how often that answer differs from the one you were about to give.