You Luddite!

I'm joking of course. Maybe it is because we farm in NE Missouri, but I couldn't agree more with what you said 

First off, I can't see why building P and K levels to a high level is necessary across all soil types. I can have a 300 pound Potash and a 50 pound phosphate level but if it is in a Lenard or Armstrong soil type here it would be a waste of money. Water always has been and always will be the limiting factor on what kind of crop we raise on these soils. I have a report from the Potash and Phosphate Institute that give expected yield results at different test levels. In Missouri a 240 pound K test will give you 96 percent of potential yield. I can't justify increasing K levels to 300 pounds to achieve another 4 percent in yield. P levels are similar for both corn and beans. 

I fertilize for APH level yields. We also variable rate our pre-plant by soil type. Five years of Climate Fieldview have shown us on average our best laying soil, Putman, will be our best yielder. Mexico will yield about 90 percent of the Putman and our Lenard and Armstrong will come in at around 75-80 percent of the Putman. Our fertilizer is applied based upon these numbers. 

I just sampled every field we farm this fall and pulled one sample for about every 25-30 acres. I know, after 47 crops on most fields, where the differences lie. My only reason for the test are for liming. We have our own spreader and generally apply 2 ton per acre when the Ph gets below 6.2ish. 
I've pulled soil test before on a 100 x 100 grid. That is about 1/4 acre. I pulled five samples. Each corner and the center. The results showed that there was variability even within that small of a grid. So, that begs the question, how accurate and uniform can a 2.5 acre grid be when my smaller grid was not uniform. 

My thoughts are once the technology exist to get real time soil analysis as your spreading P and K then you will have something. Maybe our experience is different since we don't live in an I state also.