How strange! In some games, it is artificially filled with the noise of crowds to make the audience feel the excitement. Many leagues-the Champions League included-start recording the fans' soundtracks before playing the game to make the game exciting for viewers who do not set eyes on it during the pandemic. The arena may not be so packed or scanty. That's not all Training is still yet to disappear. This is very true, especially in tournaments with only a few participants.
I coming to that. The sound to me is for viewers delight and pleasure. During the COVID-19 pandemic, most interlian leagues were very scantly viewed but the sound was appearing as if the field was filled in full spectacular while the camera showed very open spaces on the seats across. We only saw coaching crew spacely and very few people who are very much distant very one another. So it is an observation that op has made and I believe the much of the noise is traditional to make the viewers have a feel of the game even when they are not there. And it is equally a business strategy to entertain people so that they bring their adverts onboard.