Well somebody has to move. So it is 50/50 if I should or they should. So...nice to say thanks, no? FGS? Not really difficult is it.
YABU, whilst someone has to move:
It should always favour both the person most able to do it, so the fit active person already primed for exercise.
It should always favour the person using the facilities less for the designed role - so on a running track, the pedestrian moves, on a pavement, the runner moves.
And in any case, there's absolutely no reason to expect thanks for something you acknowledge you've chosen to do.
Equally as part of normal social interaction its good to acknowledge people when they're in your environment, even if they do what's expected of them, it's nothing to be annoyed about if they don't though, you never know if they have the same social conventions as you, or if they're hugely distracted or anything, just carry on.