Both of my two have been the same. My almost 3yo, I've only done hers once or twice but only a few toes. I have always assumed its because they spend so much time crawling and in bare feet that the ground kind of files their toe nails? No sure if that's true but that's what I've always assumed.
My daughter is 22 months and I have only barely filed her toenails once or twice when they’ve had some sharp spots!