@Fd,
Is that water filter available with a pink tube top and a mini skirt?
Depends on how well maintained the municipal water system is and the plumbing in your building. Some buildings are made with "galvanized" iron pipes which, contrary to the galvanization, rust away from the inside out. This will, unfortunately, contaminate your drinking water with excess iron oxide precipitates and potentially other metals, some heavy ones, depending on whether any of the plumbing was welded together. If you have copper plumbing, you're probably in good shape except that most municipal water mains are made of iron and wherever your copper plumbing and the municipal water supply pipe come into contact, you eventually will develop corrossive reaction which, again, will contaminate your tap water.
Some municipal water systems are now surrounded by excessive land development which, in turn, may contribute to contamination of the water runoff into the reservoir that holds your drinking water, anything from naturally occurring animal waste to industrial runoff, including the stuff you use to kill pests and weeds and to fertilize your lawn and, at worst, raw sewage.
So drinking bottled water may or may not be stupid. It all depends on where you live and how good your municipal water supply happens to be.