I cannot give you better reasons than this article does:
Twenty Benefits of Drinking Water
The article is both inspirational and motivating. Many of us might look at many of the points given with skepticism, which is very obvious and healthy thing to do, but slight experimentation would not do much damage, especially if you're already aware of Hyponatremia and you don't drink too much of water too fast in your experiments.
I have observed that keeping a water bottle handy increases our water intake. It's because we're not very motivated to move too often to drink water, which seems such a trivial thing. Moreover, going to urinals too often becomes a compulsory if you drink too often and that seems to be something to be managed, especially if you're engaged in something which needs sustained focus. Most trivial things become key points and even life altering factors in our lives if neglected long enough. My suggestion is to give this article (link above) a thorough read and it will not harm you in any way. It will hardly take your 10 minutes even if you are the slowest of the readers.
I feel that most of us drink less water than our bodies need. I observe people most of the time overlooking this vital factor in their busy schedules. It will not be long enough to observe changes, positive and vital improvements in your health, once you start increasing water intake in your routine.