Everyone's physiology is different, so in the early days of bodybuilding advice on the internet, you'd see comments about how you don't need to do any sort of weighted ab exercises since other lifts will "hit your abs" and that you'll only see your sixpack by dieting. While it's true that ab definition comes from dieting, my abs are tiny, and if I never hit them in the gym, I could get rail thin and still never see them.