Often HR tends to be taken for granted. Any common activity, event, appointment that a business manager needs resource on, the first ring goes to the HR guy. Now, Iam not saying it is wrong to be resourceful. But not at the cost of being taken for granted.
I have found it very useful several times to direct people once and if the requests repeat, polietly show them the right direction than try and please just to be "in the good books of". What happens on the practise is, after a few repeats, it becomes a KRA with out even us realising it.
I would prefer to focus on HR activities than run errands. I have noticed this trend especially in unit level HR roles where a decentralised HR team reports into a business line manager who uses them as extended secretariat.
I have been several time consulted by HR colleauges, who have undergone this situation. Leadership, they feel is also to be available, but dear friends, Leadership is also about being a leader and not a messenger boy.