i'm pear-shaped and i've never had a thigh gap. that's just not how my skeleton goes. i've ranged in bmi from 17 (i had an awkward puberty where i grew faster than i could eat) to 21 while pregnant and the tops of my thighs have always touched. but just because it's unobtainable for my frame doesn't mean it's unobtainable for many many women. if you have hip/leg shape for it, you'll 100% have it if you're at a normal weight. if you don't have that frame, that isn't an excuse to get fat.