I think the reason for the high nitrogen has to do with the mulching mowers. The clippings when breaking down will absorb a lot of the nitrogen. Also the soil here as plenty of phosphorus and potassium. A soil sample would give one the "key" to what is needed, but then there's the time and expense (and the give a sh*t) to do it.Back in the dark ages, my father always tended toward balanced lawn fertilizers as opposed to high nitrogen. And it always produced good results.
These days, the balanced can be harder to find. Everything has high nitrogen and no phosphorus.