My thoughts based on what I read here and observe elsewhere.
4x4 trucks sit higher than 2 wheel drives by a fair bit. So if you don't want to raise the trailer don't buy another 4x4 as the new 4x4s are simply too high. I had to raise my new mobile suite 2 inches and 3 may have been better but everyone was concerned about the overall height and the steps. The trailer manufacturers I blame for not keeping in tune with the truck manufacturers. If they built them with the riser it would be simple and free to adjust the hitch and or pin box for the lower 2 wheel drives or lower older trucks.
Possibly the trailer manufacturers look at purposely as a money maker to do the lift later.