Often enough, it's because of safety regulations. Both of those cars have steel dashboards, for one, and then they also have no air bags in the steering wheels. Or are you just referring to the general aesthetics? The 2001 — 2005 Ford Thunderbird is an early 2000s car that has somewhat of a late 50s aesthetic, in a way; it's mostly due to the tail lights, circular side windows, and interior:
@BarryFromMars I'm mainly thinking interior, plenty of cars have interesting exteriors. It's still possible to have an interesting/crazy looking interior while still being safe. Yes that fury's steering wheel has no airbag and the steering column probably rams straight into your chest if you crash, but interesting and safe aren't mutually exclusive.
@Snow oh yeah though, subaru justy aint a shitbox at all. that thing can climb muddy, snowy and gravely places like a champ, with good tyres on it ofc (cuz 4x4). same story with fiat panda and lada niva