Please tell me why people go home immediately when a soccer match is 1-0 or 2-0.

For example, I saw how Lotte fans all exploded in despair and eventually went home all at once when they were losing heavily by 9-0, like in the last KT Cup match... I can understand the feelings of those Lotte fans a thousand times over..
In contrast, in soccer, for instance, when a team is losing 1-0 or 2-1 until the 30th minute of the second half, why do people just go home instead of staying to see if they can score that one goal? An equalizer could still happen..
Also, I see some people who go home right after the first half if they are losing 2-0; why do they go home just because they are down 2-0 in the first half? You have to see it through to the end to know..
Please tell me the reasons why people leave and go home without watching until the end when these two situations occur in soccer.