Oh yeah, definitely a great point. Water may seem similar enough from place to place, but that's far from the truth. There are massive differences in chemical content and those differences have a huge effect on taste and body of the final beer. Water in England & Ireland, for example, has unique levels of carbonates and calcium which balances out the heavy acidity of roasted grains. Because of this, they have always been famous for having the best porters and stouts. Now of course, brewers typically doctor the water up by adding and removing whatever they want to artificially get the water to where they want it to be, but when it naturally has the perfect content, it works a lot better.