150K is not low mileage.
It seems the American public got what thy wanted.
Less emissions, longer lasting, less maintenance.
Now it just cost a bit more than in 1970.
I will start with the wonderful transmission. Anyone old enough to have purchased a car PRE 1970 knows that a transmission fluid change was never, ever, called for in the maintenance book. Transmission fluid changes once again began to die off in the 90's. What happened from 1970 to 1990? Well, they stopped shooting whales and then synthetic trans oil came about. Pre 1972, Sperm Whale oil was added to trans fluid and changes were not typically called for. Once the anti-tree huggers stopped shooting whales, trans services came about. I cheated, I added LubeGard and ignored them. Beyond that, a trans cooler is not out of the question.
As for the engines, better metals used, direct injection and easier starts means shortened cranking times for the start up.
Synthetics oils also play a large part.
However, in the old days, a yearly tune up was not unheard of. Now it goes out how far? And cost's how much? But you did get lower emissions and (ha-ha) less maintenance.