yeah, that makes sense. these things would certainly diminish the usefulness of a simple "go this way" indicator. but not to the point where it'd be entirely useless, i think. even if i don't directly follow the indicator, being able to tell where my ultimate destination is might still be helpful to choose what path i want to get there.
if it's just a single marker than shows a small icon indicating direction and maybe distance, it shouldn't be a problem for the UI, even when it isn't used all the time. plus, if it's set manually, you can always just not use it on travels where it's not helpful.
obviously, if something is just pointless, then dev time shouldn't be wasted on it, regardless of how unobtrusive it is. but i don't feel that's the case here.