The reason for this is the soundboard
It is made of soft timber called Spruce and good Spruce is very, very, very scarce. The soundboard has enough inbuilt tension to hold an upward curve of 7mm against a pressure of some 450kg.
Violins continue on for years because
they are better housed and away from
climate change, combined with the
fact that there is a soundpost for
support. The piano soundboard has
no support at all