I have a really boring musing about stretch marks as I was just admiring mine whilst sunbathing in the garden and wandering around mumsnet and putting the world to rights! 
I have quite a few stretch marks acquired on my thighs, boobs and hips during puberty. That was a long time ago and they've all faded now. I got them because I 'developed' quickly in a short space of time. I don't have any on my stomach as a result of pregnancy.
My 15 year old daughter was showing me hers last night. She has them on her hips, thighs, bum and boobs for the same reason - puberty. She entered lockdown looking like a little girl and came out of it most definitely a woman.
No one has ever commented on them until a couple of years ago until a man I was seeing asked if I'd put on/lost a lot of weight in the past. I hadn't/haven't but he didn't seem to believe me and said he'd never seen/noticed stretchmarks on a woman before (he'd never dated anyone with children). He really believed I'd done setting out of the ordinary to get them. I thought most women would have some at least.
Obviously he was an idiot
but I just wondered how common it is.
Tell me about your stretchmarks! (Exciting stuff!)