Some soil blends definitely don't require you to pH your water and a lot of people who grow organic don't bother with it. My opinion, and this is just my opinion, is that you will be depleting your soil of those pH buffers faster when your pH is way off. If my water source was that far off then I would look into something you can use to lower the pH that won't harm the microbial life and will work well for organic grows. I learned a lot about how pH, Ca, and Mg interact when I had a reef tank and built a calcium reactor for it. The difference in the rate the Ca dissolved, based on how much I lowered the pH with CO2, was pretty crazy.