like sanitizing - it's important. of course. But it's also overrated. For the amount of effort, complexity, time and research it requires, the impact is not that significant - unless your regular tap water is way off in some way. So it's important to know if you are one of those people, but if you are not, it may not be worth the effort, and likely there are other things you are missing that are more crucial.
And for people who don't know what they are doing, its more likely they will mess it up in some way.
I would say for 90% of beers and 90% of brewers, using your own carbon-filtered water, or perhaps cut 1:1 with RO water will work just fine.
Sure, I often make subtle adjustments, mostly for stouts and pale ales, and I even measure pH once in a while, but in terms of ratio of complexity vs. taste improvement, it's going to to up there with decoction and turbid mash.
Not a knock on anyone using it - if you are educated enough to understand pH buffering and know the difference between sodium bicarbonate and calcium carbonate and how each of those additions influences effective hardness - just as one example - great! you should totally do it, and it probably makes a difference in your beer - because you already exhausted all other areas of improvements.
But for most regular brewers it's too complicated and is overkill. That's just my opinion. I own 3 pH meters, and 5-6 different packs of mineral/acid additions that I use once in a while, but I wouldn't recommend it for most brewers who are not already super into water chemistry.
In fact, I bet a large section people who think water treatment improve their beers, do that due to placebo effect (you spent all this time and effort and money - it must be better), and that another large section (overlapping) makes their beer actually worse if they just took their chlorine-filtered tap water.
