It’s a bit fuzzy, but that doesn’t distract from my point. Playing fetch with a dog gets messy. Tennis balls especially collect moisture, dirt, and debris. The happier and more exhausted the dog is, the more grime you’ll find in the cracks of your hands and under your nails. The cracks come from frequent washing and use of disinfecting wipes and cold, dry air. I can’t change the weather, but I can try and reduce the amount of space available for gunk to cling to by not letting my nails get as long as they are above. My nails might be long and sturdy, but those qualities are not helpful when animal sitting. Dogs don’t care how long my nails are. They care that I’ll throw their various toys constantly, no matter how filthy I get.