If the rules of the game are that we only act out of self-interest, then I would only praise you if it directly benefits me in some way. Is that the sort of relationship you would like to have with everyone in your own life?
If you've oversimplified psychology and behavior that much there's no point asking "why" anyone would praise anyone.
You had as an unstated axiom that self-interested action are not praiseworthy. You still have not made an argument for that, though you have pointed out that a world composed only of self-interested action would be an unpleasant one (I agree).
However, using a more realistic understanding, where actions come from a multitude of motivations, why do you consider a given action's being self-interested to exclude it from praiseworthiness?
Sorry, the post I responded to asserted that “our motives are ultimately guided by our self interest”. It seems like you are now applying my words to a different context.
You had as an unstated axiom that self-interested action are not praiseworthy. You still have not made an argument for that, though you have pointed out that a world composed only of self-interested action would be an unpleasant one (I agree).
However, using a more realistic understanding, where actions come from a multitude of motivations, why do you consider a given action's being self-interested to exclude it from praiseworthiness?