I Yet never actually grasp the real-world, useful significance of the steps, the PGs, the RNT values, etc..
Useful significance? If you watch your computer during a couple of boat dives you quickly get the fact that
-deeper you are the less NDL
-shallower you are the more NDL
-On dive 2 you will start with less NDL.
-The longer dive 1 and the shorter the SI, the less NDL on dive 2.
-on the hang bar your NDL is essentially infinite.
-safety stops are a good idea.
The tables are just a not very accurate conservative heuristic to talk about those things.
I can use tables and have them with me. I do not find them that useful for the kind of diving I do. Note that I do diving from a fixed location be it boat or shore. I do not do diving where we have to get some where and have enough gas to get back. Thirds are always an option for me.