Speaking from where I live as a few forum members are from Canada, among other places.
A simple set up indoors with an AM transmitter with the wire and maybe a ground through the a/c cord won't get you as far as FM will. Probably the majority of people don't have the access or facilities to do the not so easy outdoor install with ground radials etc to get the extra range. As for another member getting such good results with the Spitfire in a building of all places with just the indoor install with no ground is exceptional and maybe is blessed with no electrical noise to drown it out. But most all over North America AM is killed by the electrical buzzzzzzzz that plagues the AM band in all houses and buildings and in the house where I am it's across the whole band and at the signal strength of the local 50,000 watt stations.....wipes out everything! Am is only good if you go outside away from the hydro(ac power) like the street. As for if something was there that people want they will listen, My brother told me that he will never listen to AM no matter what is there.....listen to this he said! If I were to be on AM here where I am it would be for MY USE ONLY as no one would listen and here in Canada there's no AM transmitter approved for "broadcasting". If my goal is to have listeners then FM is the way to go here as BETS-1 gives us increased coverage than part 15 does and in mono a little more. Also the Decade MS-100 is approved for "broadcasting". So here, the statment that a medeocre AM is better then the best FM is not true. And if you don't have access to the ideal AM set up....not medeocre, FM gets you farther and doesn't have to fight through the noise to do it.
FM is also much easier as a good FM set up needs only an indoor place on a shelf and works with a indoor antenna thats 30" long and there's no ground involved. Much simpler for someone to do.
And then there's the nightime thing.....forget it....even the best outdoor set up with a compliant transmitter looses the range at night drowned out by the clutter of 5 stations coming in on top of you. FM doesn't....it works day and night.
I grew up with AM and in the 60s and 70s....and eighties for oldies and it was clean. but in the mid nineties all the noise started creeping in till you have what you have now and this is what kills AM. I can't listen to something that I want it's so bad here.
Here in Canada FM IS the practical choice if you want more than yourself listening.
Even in a rural area out in cottage country where I had listeners around me no one would have listened if it was AM.....most people had there radios in their garages or porches by their cottages and the noise was brutal even out there and no one would listen through that. They would have to be right beside me to get a clear signal.
AM to me is a last resort only if for some reason I couldn't do FM.
Mark