I've often seen it in answers and comments on this site, that if you want to sue someone, then just go ahead and sue, don't tell it them beforehand. It's often repeated as some kind of dogma, I've never seen explanations for it.
So, what are the exact advantages of suing someone without warning? I doubt it's the effect of surprise, and they will have plenty of time to consult their own lawyers before anything crucial happens.
That the following example: Alice wants to sue Bob, because he caused her some damages. The damages are high enough that she wants to be made whole, but not as high that a lawsuit would be surely expected. Let's also assume that both know that Alice will have very good chances of winning if it comes to a trial. At first Alice asks him nicely to be repaid (without mentioning a lawsuit), and Bob refuses because he thinks that Alice won't bother suing over such a thing. At this moment Alice could say that if he doesn't repay the damages she will sue. Bob would then have an incentive to pay, as he now knows that Alice is likely to sue and if it comes to that, he will likely lose much more (legal fees, time, etc.) So it would be optimal for both of them if Alice tells Bob that she will sue, as both of them would be saving time and money if he just paid her without going to court.
So, in the above situation, why should Alice just sue Bob without first threatening/warning/telling him? What would she lose by trying? (and is there a difference if the jurisdiction does or doesn't have a "loser pays both parties legal fees" policy?)