I have water in the coop and in the pen. Each morning when I let them out of the coop, they run around a bit to get the sillys out of their system, and then they head to the outdoor water can and drink, all five of them. The water (plastic one) can in the coop is seemingly never touched but the food dish is. The water cans are filled the same time so one is not fresher than the other. Also, do you have food both inside and outside the coop? I lock my birds in at night.
Mine were excited about drinking a mud puddle instead of the nice clean water in their waterer. There's no accounting for taste. You don't need to have food and water in your coop if you are up at dawn to let them out. But if you don't get right out there, I'd keep at least a small feeder and waterer inside.
Why did the chicken cross the road? Because what ever is over "there" is always better. That's just how they are. Make sure you keep the waterer clean and free of algea and if they need the water, they will drink it.
