The way I look at it, there's no water profile that's perfect for all styles. If you only like to brew a limited style range, and your water works for that range, then sure. But even as an extract brewer, water can cause off-flavors so tap water should at least have the chlorine/chloramine removed (carbon filtration, campden tabs, whatever), but beyond that it's not critical (but still could make the difference between good beer and great beer with extract brewing). With all-grain it's a little more important, but again if your water is middle range enough that you can slide with pH on both light beers and dark beers (that's tough to do though, and in both cases pH would necessarily be towards the opposite end of what you'd ideally want for the best beer), then again fine. But ultimately you won't be able to consistently brew any style you want up to the highest quality levels without dealing with your water. If you want to brew your absolute best no matter what you're brewing, it's something you MUST tackle period.
That said, water's complicated, and if you're happy with your results carry on. And even then, unless you're brewing to the absolute extremes, or have absolutely TERRIBLE brewing water, you can often manage enough with most water sources to make beer for most beers. As such, water's probably one of the last things I'd tackle.