Does the flavor of lemon in your water make it pair better with food? I think not. If anything it distorts the flavors on your plate.
Water should be neutral, that is the idea. It should cleanse your palette, not inform it with another kind of acidic flavor.
The earth is 75% water, our bodies are as well. Just regular water, no lemon! Who could argue with that? When you drink water, you are a part of a huge cycle of evaporation and condensation that has been going on for billions of years. All without the addition of a single !@#$% lemon!
But you are fancy so you need lemon for your precious free water, is that right?
You know what really tastes better than water? Wine, beer or a cocktail. Try it.