The simple explanation is that it's not a linear relationship. There is a lot more going on than most people realize in terms of energy systems. Doing a 1rm or a 3rm is going to utilize a totally energy system than doing 10 or 12, and doing 20-25 is going to fatigue you through different mechanisms again.
The complicated explanation is more...well, complicated.
The low reps (1-3) probably mainly uses the ATP/Phospho-Creatine system, and doesn't really use a lot of substrate like glucose because it doesn't need to and barely has the time to. If you always train low reps, this system will be trained to be more efficient.
10-12 reps will likely mainly use glycolysis, and because it's anaerobic it'll produce a shedload of H+ ions pretty quickly, but in this rep range you're probably going to stop just as they reach painful enough concentrations and have time to buffer them between sets.
In the super high rep ranges like 20-40, its still glycolysis for the most part, but maybe it shifts a little towards aerobic metabolism near the end. The main problem is those H+ ions, which aren't a linear relationship either. As more H+ is formed from ATP hydrolysis, more and more muscle tissue is going to get denatured because of the drop in pH, so the remaining muscle is going to work harder, creating more H+ and so on and so on. The weight your muscles are able to lift and the point at which they can't lift ANYTHING anymore don't necessarily have to match up.
Basically, if you never train at one of those specific rep ranges, you aren't prepared for it at physiological level. The more you train at those rep ranges, the more efficient you'll be due to higher expression of the required enzymes or better substrate storage.
If a sprinter can run 100m in 10 seconds it doesn't mean he can run 800m in 1:40 or the 1500m in 2:30. The 800m is technically possible but unlikely, and the 1500m is just not a possible time. The reason for this is the same - they are totally different in terms of training, energy systems, and physiology.
People would never assume the same sort of illogical shit about other sports as they do about weight training.
So yeah. This turned into a bit of an essay.
Nice post until you hit the condescending bit at the end. Of course no one expects weightlifting to be linear. Somewhat trigometric (taking the limits of the body and the law of diminishing returns, for example) , possibly, but not linear. And I, for one, was not assuming "illogical shit" about it.
I was asking about relationships between various weightlifting patterns. And yes, I would assume that my 185 and 155 lb lifts would at least be different. Why they weren't is what sparked my curiosity.