I'll try to explain a bit better why this matters to me and probably some others; no criticism of those who see things differently, just an explanation. Live entertainment (sport, music, theatre) is unique, as it depends on the interaction of performers and watchers. The crowd/audience are part of the event, and the greatest experience at a match is when crowd and team are together as one for 90+ minutes. For those minutes, nothing in the outside world matters, and we believe we can motivate players, influence referees, put off opposition players, etc. All an illusion, perhaps, but that is why watching a match at home on TV bears no comparison - it may be warm, dry, comfortable, drinks easy to get, etc., but the tv viewer is not part of the event. And the rest of life still intrudes easily - at a match, especially under floodlights, your whole focus is on the game. And the performers, no matter how rich they are, like all actors, singers comedians, feed off audience reaction. Canned laughter is no good to a comedian.
Especially recently, the connection between players, fans, club has been fundamental to our success, and I like the illusion that I/we are part of it. Actors, comedians, singers will all be disturbed by the audience leaving during a performance, and I imagine footballers are no different - they sense and respond to a crowd; and similarly, it is difficult for the crowd to come together if some are walking out when the match is still going on.
That is not to criticise those who have to leave, which I understand; or to criticise those who choose to leave, though I still don't get why they do it.