This isn’t reckless—it’s calculated.
For you. Because your body is used to it. And so far you haven't been unlucky.
How much water someone needs during physical activity can vary a lot, different base levels and then differences based on habit.
But no one has ever died from carrying an extra bottle of water. You may want to get your weight as low as possible, but carrying another 10lbs of water is just extra training. It literally helps you in the long run.
If you're taking the absolute minimum you need, and any substantial setback happens, you're fucked. On a long enough timeline something will happen, even if you make it out alive, a sprained ankle 10 miles from help sucks enough when you're not gonna have to be dehydrated.
Just bring another bottle of water.
Even if it's a "safe" gamble in terms of chances it goes wrong, the consequences of it going wrong could literally be deadly.
Hell, imagine you're 10 miles away from help, completely fine, and you come across some idiot who desperately needs water. An extra bottle could be the difference between you saving a life, and walking away from someone you know won't make it out.
Don't play with shit humans need to live.