This is rarely a defect of the piano as built, and more that people don't realize that pianos NEED an environment with a stable humidity of about 45% year-round

This is rarely a defect of the piano as built, and more that people don't realize that pianos NEED an environment with a stable humidity of about 45% year-round. This is true of any wood instrument, a guitar being one most familiar to folks. There are humidity control options for smaller instruments, too. All kinds of damage can result, such as sunken or collapsed tops (especially arch topped instruments that can be under a lot of string pressure, such as mandolins) or cracks as in a piano's soundboard. My solution was to move to Seattle where our house generally stays at the perfect 35-45% humidity, and all the instruments are happy.