My2015 Sierra has the steps, my '04 Ranger doesn't. Yet when I back them up tailgate to tailgate, they are the same height. Sometimes I put a section of my ATV ramp up, if I am going to be loading the pickup bed.
...something about small peckers and compensating or some such baloney. Bet the car makers know why.
I reckon that it's supply & demand. More urban purchasers wanting jacked up height = can see farther in traffic and are more prominent (look at ME!!!).
In other words, the 'pick-ups' (utes) are drifting away from being practical work vehicles.