Easy - it is illegal to smoke on a platform.I'm sure I heard or read somewhere that smoking is illegal anywhere on railway property but maybe I'm mistaken.
As for people saying this is pathetic, well yes but a passenger is likely to say telling them that they can't smoke at the end of a deserted platform is pathetic so where exactly do they draw the line?
It is not illegal to smoke on the track.
FWIW I would not object to someone smoking on the end of a deserted platform either.