You give tochacha or any other advise if someone will likely accept it and if your tactful enough to do it right and not have it backfire.
This applies to comments made in other situations as well, like paying a Shiva call. People say the dumbest things sometimes or deal with things on a level they are not qualified to do.
For example: I was at a Shiva house, for someone I’m close with. who lost a child. This guy, relatively young who had Smicha, was drawing out every emotion he could thinking he was helping the father deal with it. He didn’t know when to stop, so we had to force him to quit. This guy once saw a Godol in a similar situation and thought wrongly that he could do the same thing.