It's not laughter, but that particular audience reaction when a popular character enters (applause, cheering, even "barking" noises) in sitcoms is unnatural and essentially breaks the fourth wall. The earliest show I recall doing this was Happy Days, which started with Fonzie entering to applause and cheering then graduated to practically every cast member getting that treatment. Obviously Garry Marshall liked it because no one discouraged the audience from doing it, nor did they edit it out. HD only had the brief applause/reaction thing happen though, while Married With Children took it a few steps further by encouraging the hoots and hollers all during the taping. MWC was buoyed along by the generally raucous audiences who enjoyed the show's trademark lowbrow humor. People who went to watch a taping of MWC were encouraged to behave that way because....well, prudish people would not have been pleased to be there.
One interesting comparison would be two late-1970s soap opera parodies: Soap and Mary Hartman, Mary Hartman. Soap was taped before a live audience while MH, MH was not. Both were hilarious spoofs of the soap opera genre, but whereas everyone laughed along with Soap and knew it not to be taken seriously, many viewers of MH, MH were left confused and unsure how to take its deadpan delivery with no laugh track or audience reaction. The laugh track seemed to give the audience the signal that it was okay to laugh at these people and their predicaments.