Shops love selling them since the margins are great, the local government loves them since it brings in additional tax revenue, and the tourists love them since they don’t want local bacteria to interfere with their enjoyment of authentic experiences. 67 million barrels of oil is used every year to produce and transport them enough to fuel four million cars for the whole year. While traveling, I usually fill them before leaving a safe place, for example, a hotel, hostel, or a restaurant, so that, I am not taking the risk of consuming unfiltered water or ending up on a remote island where there is no water fountain.