Now there's a dissertation topic for a grad school flunkie in media / gender studies to pursue. Look through the kissing scenes from the top 10 shows in the Nielsen ratings for each year, and measure how great the audience response is. Of course it's a silly project, but it would be an actual result that somebody might find interesting -- unlike whatever else those people are thinking of for their senior thesis or dissertation.
I was hoping somebody else had already done this work, so that I could just link to them. But nobody seems to have noticed or felt it was worth writing about. Well, they do know what the phenomenon is, just not whether it's stopped and why. TV Tropes has an item about it under the vocalizations expected of the Studio Audience:
WooOOOoo (rising and falling tone)
This is for romantic moments. Like, after three seasons of Will They or Won't They?, the couple finally have the First Kiss. Or an established couple have a bit of dialog with some innuendo and run upstairs to the bedroom together.
This used to happen all the time on teen-and-tween-oriented shows, especially Saved by the Bell. Here is a typical example from a 1992 episode. A quick check around YouTube for something from a more recent teen sit-com came up with this clip from a 2012 episode of iCarly. Man, is that weak! Barely even gets off the ground. Not to mention lots of nervous laughter ("awkward!"). I clicked around the "related videos" to see other contempo kissing scenes, and this one seems to be average or above for level of emotion coming from the audience. Often they don't react at all, or again with only nervous giggling.
What was all that wooooo-ing about, and why has it stopped?
It only or mostly came from the girls in the audience -- the guys didn't shout out "all right!" or whatever. And it was always directed at a female character. How can you tell, when both the guy and the girl are kissing? I don't know, but you just can! The female audience members are empathizing with the female role, so they're letting out the expression they would feel if they were playing that character's role. And it happened whether the girl was the recipient or the initiator. So it wasn't so much about what particular role she was playing, but about the end result that she was locking lips with some dreamy dude.
Girls sure used to heat up easier, didn't they? All it took was seeing one little kiss between actors, not even real-life maker-outers. The swelling, then calming tone clearly echoes sexual build-up, climax, and coming-down. And the swooning chicks in the audience weren't cherry-picked from the local slut brigade -- that's just how the average all-American girl responded back in the '80s and early '90s. Not keeping it to themselves, either, but erupting in a chorus. "I mean, we're all feeling the same thing, right? OK, why be all shy and ashamed then?" Note that they used to feel unashamed of something basically wholesome, if unsettling-to-their-fathers, rather than unashamed of off-putting character flaws like they are today.
In fact, now they're more likely to not respond at all. I can't tell if that's because girls these days are more autistic and have trouble empathizing with the actress, or if they just don't sense much passion playing out before them, and feel little there to resonate with. Likely both. When they do respond, nervous laughter is almost guaranteed. Any expression of anxiety (laughter or otherwise) is a form of heightening their self-awareness or alertness, which slams the brakes on whatever ride they could have been going on. They can't turn off their internal spotlight and get lost in the moment. No catharsis.
What about the fact that it's nervous laughter rather than nervous coughing or awkward silence? If it's laughing-at, then they're trying to send a signal of derision, contempt, sarcasm, or otherwise "being above" something as silly, trivial, or dirty as feeling passion. It's not dripping venom, but even a subtle expression of superiority gets the point across -- don't try to get me excited, because my body and my brain just don't work that way. If it's laughing-with, then it's part of the larger pattern young people have of pointing out their own awkwardness, and trying to get others to laugh-with, so that none of them feels too pathetic for being so awkward. To my ears, it sounds more like laughing-with, so the audiences are communicating, "I know, right? We are too awkward to enjoy kissing, smh."
I'll leave it as an exercise for the readers to find out when all this woooo-ing began to rise toward its culmination on Saved by the Bell. It's hard to find specific scenes on YouTube, so searching for "Brady Bunch kiss" didn't turn anything up. But maybe messing around with the terms will uncover something. I do remember it being a staple on sit-coms of the late '80s, though. And was it only on teen-oriented shows, or would the Mary Tyler Moore Show have had it too? Or Laverne and Shirley?