Piano performance is an art. Like all live art, there's a visual element. The visual is why Richard Clayderman is so famous. But, of course, the very best are judged by their playing, not their appearance, but it doesn't hurt to look good

! Also, NO MATTER WHAT YOU DO, you have to be healthy. You could be the best pianist, or painter, or CEO, or whatever, but when you drop dead of a stroke or heart attack due to lack of exercise, everything goes down the drain. Exercise provides energy, which brings only advantages to piano playing.
But of course, jamming your finger, or bulking up your arm to the point of reduced flexibility and agility, or lifting so much weight that your fingers are constantly tensed and stiff will cause more harm than exercise will do good.