Should officials help players?

A few days back there was some controversy at the US Open (Tennis, not chess), when the chair umpire came down to give Nick Kyrgios a pep talk during his 2nd round match. Kyrgios picked up his form, and went on to win the match. This sparked a discussion about whether the umpire's actions affected the outcome of the match, and whether it was the correct thing to do.
This question occasionally pops up in chess events as well, when arbiters are called upon to help players. At junior events this can often go as far as calming down upset children when they blunder, but it also happens in open events.
The most common case is making sure players follow the rules. An example from a number of years ago was when a player asked me what the correct procedure was for claiming a draw by repetition. If I refused to answer there was a chance that he would do it wrong and be penalised. If I did answer I could be helping him save a game that he otherwise may lose. So essentially my decision would affect the result one way or another.
I did explain the rules to the player (which the opponent had no problem with) and if I recall correctly, he realised his draw claim would be invalid under the circumstances, and played a move as normal. Since then the Laws of Chess have been updated to deal with this situation, in that players are now entitles to ask the arbiter to explain any rule (and I used this example in helping draft the new rule).
This is probably as far as I would go though. Certainly reminding a player to press their clock is a step to far, but there is still a bit of a grey area. If you saw a player touch one piece but then move another, would you wait until they pressed their clock to intervene, or say something straight away?