This is because of the varying concentration of the total dissolved minerals in the water .
When we see that the water is tasteless that's means we are talking about the pure water which don't have any taste. But the water we drink have the different amount of minerals and dissolved solids in it which impart the taste in water, and because different place water have different concentration of mineral so their taste also differ.
Moreover these mineral are important for human health also but upto a level that's why in a water in bottled we buy from market is known as mineral water. Also, each company mentioned the concentration of minerals on the mineral water bottle.