Recorded or live audience laughter was standard in television comedy for decades and is now unusual. The device disappeared because the conditions that made it useful changed.
The device came from radio and theatre
Comedy was originally performed in front of an audience, and broadcasting it meant broadcasting the response as well. Laughter was part of the recording rather than an addition to it.
When production moved to studios, keeping a live audience preserved that dynamic, and the multi-camera setup was designed so a room could watch the performance as it happened.
Recorded laughter was introduced to smooth the result, filling gaps where a joke worked on screen but the room had been distracted or the scene had been reshot.
Single-camera production removed the audience
Comedy increasingly moved to a filmmaking style with location shooting, multiple setups and no possibility of an audience watching a continuous performance.
Added laughter over that style is conspicuous, because the visual language implies observed reality rather than a performance for a room.
Viewing conditions changed the function
Laughter helps a solitary viewer by supplying the social cue that a room would otherwise provide, which mattered when television was watched live at a scheduled hour.
On-demand viewing on personal screens weakened that need, and audiences accustomed to comedy without cues began to hear the laughter as instruction rather than company.
Performers and writers also disliked the constraint, since a track imposes a rhythm of pause and reaction that limits how quickly dialogue can move.
Timing rather than sound is what changed
Comedy written for an audience leaves space after a joke, and that space is audible as a gap when the laughter is removed.
Single-camera comedy fills the space instead, layering jokes and letting lines overlap, which is why the style feels faster rather than merely quieter.
The format survives where the audience is real
Shows still recorded in front of a live audience continue to carry laughter, and the multi-camera form persists because it is efficient and suits certain performances.
The distinction now drawn is between genuine response and sweetened response, and productions that keep an audience tend to say so explicitly.
What has genuinely ended is the assumption that a comedy needs laughter to be understood, which was never proven so much as inherited from an earlier medium.