Something to remember about oil analysis, the metals content portion is more for an early warning that something is coming apart than a "your oil is still good" indicator.

Engines with good fuel control allow for longer oil change intervals. Changing modern oil every 3 K is excessive for a car with even decent fuel control. However a car with a carburetor / really poor diesel injection / piston ring wear probably isn't going to benefit from synthetic since the oil will become contaminated before it wears out.

In theory, a car with a 10 QT oil pan could run 2X between changes over a 5 QT system further making over frequent oil changes unnecessary.