Lotta philosophical reasons as siblings to my reply here, and many of them are very fine. But let me give you a practical reason this forgiveness works out well: If you want to leap straight to aggressive compliance, you're gonna need a lawyer. That will cost you. So in a world where the choices are "ignore the infringement" or "aggressively enforce it", you've got the choice of either ponying up the dough up front, or losing your licensed rights. Now, sometimes reality hands you a bum deal and there's not much you can do about it, but that's a bum deal.

If you add a third choice of "politely ask for them to comply first", then you've got a free option, that is likely (albeit not guaranteed) to produce good results, and as an added bonus, if the company blows you off you are helping your eventual lawyer-involving case when it comes time to prove they knew and infringed anyhow.

So unless you've got bored lawyers sitting around who are going to charge you no matter what you do, there is a reason to be a bit gracious first, even for you, the programmer of the GPL'ed work.

(And yes, this RedHat effort does not create this result; this has always been an option and IIRC most historical enforcement efforts that went to lawsuit first used this. But it answers the question, in very programmer-centric terms.)