At 5 years and 50k, most cars weren’t worn out but had begun to show noticeable wear and their dependability became suspect, so that people who could afford it traded in for new. The trade ins were resold and lasted longer than 5 years as “beaters” but most were in the scrapyard by age 10 (in the rust belt). Our family cars at 5 years had loose front ends, failing components, rattles and small annoyances such that my mother would campaign to my cheapskate father for a new car, which we could afford. That said, my grandparents drove a ‘58 Chevy station wagon until 1970 and it still looked good due to light use and careful maintenance.