It might seem silly to you but it doesn't seem silly to me.
Quarter sawn wood is more stable and looks better when finished. Its also more expensive. Plain sawing a log yields more lumber per log. When you're looking for a way to make a product less expensive is to use less expensive components. Walnuts are also less expensive than rosewoods and mahogany these days.
So we end up with a guitar that is at a price point that is in reach for lots of folks.
Just because its less expensive doesn't mean folks don't like it. Lots of people love their walnut guitars. I also have a little walnut end table next to my recliner. Love it and its a beautiful thing.
I do, however, like mahogany better.