It is quite common to see Japanese men of all ages standing on train platforms or outside a building practicing their stroke with an imaginary golf club.
Japanese men practice golf strokes on train platforms because the have no time to do so elsewhere.  
mnli hypothesis: Japanese men practice golf strokes on train platforms because the have no time to do so elsewhere.   premise: It is quite common to see Japanese men of all ages standing on train platforms or outside a building practicing their stroke with an imaginary golf club.