With seasons, if you're in trouble you're only in trouble for a short time, then you have three months where you can direct your attention somewhere else and attempt to rectify the problem before it reoccurs.
Without seasons, you can't do that. Your realm is collapsing right now, and it won't give you a breather. You don't have time to go declare a war to grab more rural regions and bring them up to shape so they produce enough food to feed your city - it will have starved before that.
If seasons were everywhere, I would believe this. They are not and this disaster does not routinely happen.
I will be frank. The food game is in theory a wonderful thing. The reality is most players do whatever they can to ignore it. We can talk about all the theoretical things it introduces, like raiding fertile lands to bring a realm to its knees, however how often do we see it? It is possible, but in most cases not practical. I am proposing the review of these systems because the hypothetical situations they add to the game are simply not being seen frequently, thus the complications they bring must be weighed against not what they COULD bring to the game, but what they actually bring to the game.
