I don't find this practise weird at all. Programmed clapping gives structure and certain worthiness to shows and spectacles. Any of you seen what happens in Chinese and North-Korean party congresses? How spontanious is clapping in American, German or Italian talk-shows, as far as I know they are equipped with huge applause signs that are lid at pre-programmed points. Or again been watching teen movies, there is always that magical moment after which one kid starts "spontanious" clapping, and how weird was that in Another Teen Movie when he could not get his timing right.
Clapping seems to be significant human signal, but how often it is really spontanious? Very seldom is my guess. Meetings and assemblies are shows and spectacles in same manner as any other show, and clapping just belongs there, at proper, often pre-designed, time.
CP