It's also a reason for war! Well, I'll admit I'm one of those people that do enjoy the food game and would love to see it expanded
I also enjoy the food game... in D'Hara. Exclusively.
Food is, imo, as much as a reason for war as TMP is. Fact is, war increases the odds of production in your regions plummeting and your gold reserves available for food purchases dwindling as well. Unless you have a rural neighbor that you know you can shove around, war isn't likely to come up as a great solution to starvation.
It turns out that island-wide doesn't really matter all that much. Distribution is also very important. Basically, the more feedback we get on what the food situation is like everywhere, the easier we can tune it.
Distribution is very important indeed, especially to realms who have a deficit and lack D'Hara's trade network and agents. However, island-wide production does matter to those who overcome regional shortages by developing said networks, because it limits the possibilities for such networks to be created.
I'm not saying it's good or bad, as I can see it causing tensions between D'Hara and other importers, for example. Or, more likely, between the other importers themselves, because I'm pretty sure that the 'moot is self-sufficient and that D'Hara could satisfy itself with Barca's exports. But either way, island-wide production *is* important, it's just that the huge stocks don't make it so apparent for now.