[Barry_R]

The answer is actually "all of the above"...

Newer engines have cast in place ductile iron liners - decidedly better material than old block were made of. They often have a "spiny" or textured OD for retention in the casting so they're not as easy to replace as you think.

Newer rings are either ductile iron or steel with a plasma-moly face - - much like racing rings and very durable.

Computer controlled timing and mixture greatly reduced detonation and fuel wash - - major causes of accelerated bore wear.

Hypereutectic pistons are common in OE engines, and will last a very long time due to the hardness of the silicon entrapped in the alloy.

All of this is due to mileage and emission requirements....and the need for them to comply over 50,000-100,000 miles.