A common health myth is that people should drink at least eight glasses of water per day. While staying hydrated is important, why could this advice be inaccurate for different people? (Site 1)

There could be many varying factors as to why a person might need more or less water. They could weigh less or more than the average person, they could be more physically active(causing them to need more water), or they could be exposed to hotter climates. For these reasons, a person might need more or less than eight cups of water.