There do exist times in ballet when there is no one thing that triggers applause, but the audience has been "whipped up" to it. A case in point ....
I don't deny that applause under certain circumstances seems appropriate, but I come across those special moments very rarely. But then I have not attended many live performances. I was more concerned about two factors (1) does the sound drown the music (2) does it break the concentration of the dancers and musicians. One of the responses was interesting that some dancers may actually worry if there is no clapping (3) Does it disturb other audience members?
Most times it does disturb my concentration and breaks the spell, primarily because the music is drowned. Also, applause, like laughter seems to be infectious/instinctive. Many people seem to clap because someone else if doing so..and from watching them, it is not that they are thinking about clapping...they just do it when they hear the sound.
During a rehearsal of a Balanchine Pas de Deux at Dance Salad, I was surprised to hear a loud clapping behind me when Zdenek Konvalina was doing his Manege thingies. Well upon turning back I discovered it was Maina Gielgud guiding the time of the leaps and landings