I understand and agree with what your saying as people on this forum are normally pretty mellow and not looking to cause problems, but I would also guess that you probably don't go around posting your address all over the web either. You are of course free to do so, we just don't require or directly recommend it here.
As for the off chance someone grabs the negative attention of a nut job, why make it any easier for them? Besides, I think that it's also fair to say that there are a number of them out there without the ability or patience to track someone down to an exact location.
There are other, less paranoid, reasons as well. I personally was tracked down once via the original NPORA website. It was years ago, before I was part of the staff, before the current website and before the Member Map existed, but nonetheless it happened. Almost 10 years ago when we rolled out the new NPORA website the info that allowed that to happen was changed, for good or bad. In that case I was contacted via email by family I had not heard from in years and in that instance it was welcomed. However, today I have other family which I would prefer that they not just show up on my doorstep unannounced, if I put a pin on my house that could just happen.
But again, placing it at your doorstep, city center or not at all is the choice of each NPORA Member.