Three primary reasons:

1) The music
AIR - Alone in Kyoto

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Death In Vegas - Girls

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2) Bill Murray
God he's amazing. He's got such a perfect deadpan, and there are several absolutely perfect scenes that I'll remember forever (the cross trainer and the carpet samples spring to mind), and he really fired off Scarlett Johannsen (more on that below). I know everyone rants and raves on about the feelings of helplessness and directionlessness in this film but that's because they're awesome. Never has a film about something so alien to me (Japan, success, high class hotels, insomnia), been so relatable (awkward nights out, ennui, alienation from surroundings).

3) Scarlett Johansson
See below