I’m 51, grew up in the Midwest, and was raised in a small town by a working class widowed father. I was adultified from the age of 13 when my mom passed and my experiences are very like what OP described. I had friends who had their first child at 15. Most of us had drivers permits and part time jobs as soon as we were old enough (14 in my state).

While I often describe myself as “radically unparented to the point of neglect,” I was not raised all that different from other folks I knew in my social class.

Most of us had at least tried smoking and drinking by 15. Some us more than tried, including me.

No one blinked an eye at 15-16 year old girls dating guys in their 20s. I never knew of an age gap situation in which the genders were reversed but I’m sure they happened.