Actually... they don't. I already posted a comparison of factory service manual data that refutes that oft-repeated bogus claim.
But the most common type is still tri-metal (babbit/copper/steel) or aluminum. That had settled out by the mid 60s, though some lower-performance engines continued to use steel-backed babbit to this day.
Again, it had pretty well settled out to the current state of the art by the mid 60s, and there was virtually NO change between, say, '65 and about '98. Since the mid 90s, there's been some renewed effort in internal engine design with things like more use of die-casting processes, powdered metal fabrication processes (connecting rods being a good example, IIRC the Ford Modular v8 was one of the first to use that process). And as I said, the switch to roller cams in the 80s was pretty big in terms of gaining efficiency and reducing the demands placed on the engine oil.
I don't deny that there was a lot of progress in peripheral areas like intake manifold design, valve port design, combustion chamber design, and (especially!) electronic engine managment, all of which boost efficiency, reduce fuel quality requirements, and lower emissions. But in terms of the design factors that affect brute durability, that's largely been at a standstill for 40 years. That's the way of most technologies- rapid changes until a plateau is reached, then incremental changes beyond that. Lubricants on the other hand (particularly the high-end synthetics) have had their period of most rapid improvement during the 80s-present time frame.