Why were Motte and Bailey castles replaced?

Not all of theMotte and Bailey castles were replaced, in fact, most of them weren't replaced but were left to rot. The Motte and Bailey castles that did get replaced were done so by Stone Keep castles (Stone castles). These castles were made out of stone (unsurprisingly) but the Motte and Bailey castles were made out of wood. The reasons that some of the Motte and Bailey castles got replaced were that they weren't very strong, they rot within a few years and that they burn easily. The Stone Keep castles were the complete opposite of this.