I have two sets of experience. When I started growing in 1990 we didn't ph soil, or water. It just wasn't a thing. I was part of a network of growers of 20 dudes who were all 100% indoor and 100% clone. I'd say the soil/hydro ratio was 70/30 (soil). We used different nutes (some bottled two part/three part systems, some used bat guano and phish emulsion).
Today I'm still an indoor soil guy. The choices are much more plentiful when it comes to soil and nutes I can buy but my philosophy is the same. I didn't ph then why should I ph now? But I kept reading threads about how important ph was so I said f-it I'll buy a damn ph meter. Took the five ten minutes to calibrate it with the little packets they sent with the meter and I was off to the races. Ph of my tap is 7.0 and, according to Fox Farm my soil was ph'd for growers (without an actual number as to the number they ph their soil to "for growers"). So I ph'd my runoff instead of buying a soil ph meter. I know it doesn't tell me exactly what my soil ph is but it'll give me a ballpark. So I ph'd my water on my first watering (I didn't add nutes to my water until week 3-4 as was recommended as fox farm has enough nutes to carry a plant through 2-4 weeks of growth). So at 7.0 going in my ph meter was fluctuating between 4.8 and 5.2 for runoff which tells me that my soil was fairly acidic. But I don't ph water to get soil in range. Since then, I don't ph anything anymore. My tap is 7.0 but when add nutes it's around 6.0 (I tested it once).
But as to the point of this back-and-forth, I agree that you don't have to ph soil, I don't. But the reason I don't is because I did initial testing and I know what I'm working with. If you dont test soil/water ph initially, there could be problems. You want to test the ph of your plain water, water w/ nutes, and soil/soil runoff so you have numbers that you can adjust when necessary. Once that is done, you'r all set. The ph of your water and food will remain relatively constant. As far as hydro, I'm not gonna weigh in cause I don't grow hydro. Though everyone I know who does grow hydro says ph is important because their is no soil to act as a buffer to nute/ph/salt contents. I've heard over the years that if you mess something up in soil you can fix it. If you mess something up with hydro you kill it. Don't know if its that extreme but its part of the reason I never made the switch.