> Why do you need good clocks? For audio, even with simultaneously playing speakers, you only need to synchronize within a couple of ms unless you need coherence or are a serious audiophile. If if want to maintain sync for an hour I suppose you need decently good clock.

There are many microphones involved in a production, and humans are quite good at detecting desync between audio/video when watching a presenter talk. You cannot fix desynchronization further down the chain if the desynchronization is variable for each source.