Recently manufactured cars we own have those oil life monitors but some research shows they simply run down a milage count. The dealership even asks me what mileage I would like it set to. Sales pitch suggests that the vehicle is monitoring actual oil characteristics but in fact it is not.

What they do is calculate an oil lifetime based on running conditions of the engine. How long it's been on, what temperatures its running at, what RPM....

Point is that nobody should be changing their oil ever 3-5k.